Alright, let's start translatin'.
Disclaimer: I didn't make the drawings (because I'm terrible at drawings). The moveset ideas were a friend's and mine put together. The aforementioned friend drew the stuff you're about to see. I think the drawings help illustrate the ideas we had, however not all attacks have an illustration to go with. It's also fair to mention that he put most of the base work in this moveset (how the moves look and act) and that I worked more on the effects, stats, damage, taunts etc.
Dimentio:
Dimentio left his Dimension D and his world-domination agenda to join the brawl! Slightly taller than Luigi, but lighter than him, this joker likes to take the fight to the air and use his magic powers to beat you up!
Ciao!
Strengths:
- fast
- good aerial manoeuvrability
- attacks with magic instead of using his limbs (hence it's safer)
- good projectile attack
- his double jump goes far
Weaknesses:
- relatively lightweight
- only one of his smash attacks has good knockout potential
- despite his magic, his range isn't all that great
- short grab range
- a lot of landing lag on his aerial attacks if he lands before they're over
Moveset:
Ground normal attacks:
-Jab

A small sparkly explosions comes out of Dimentio's hand. Relatively fast, but short range.
Around 2% damage for each spark.
-Front tilt

A small Dimension D square. The range is slightly better than the jab's, but it's a bit slower. You can chain two or three of these attacks at low percent.
8% damage.
-Up tilt

Dimentio spins some magic geometry above his head. Good for racking up damage, can be followed easily by some aerial attacks.
12% damage (6*2%).
-Down tilt

A very fast, but short-ranged, attack. Dimentio flips some Dimension D squares on the ground. The higher your opponent's damage percentage is, the more likely you are to make him trip.
6% damage.
-Front Smash

Dimentio charges one of his famous projectiles before making it explode right in front of him. It's quite slow, but packs a da
mn punch!
16% to 24% damage. Ejects horizontally.
-Up Smash

Dimentio summons concentrated magic above his head. It hits quite high, but doesn't have much horizontal range. It's not too strong but it has high priority.
12% to 20% damage.
-Down Smash

In a snap of his fingers, Dimentio creates two small magical explosions on the ground, around him. It's a relatively fast Smash, and will deter enemies from attacking you with unsafe moves. It won't kill them though, and the range and recovery aren't all that great!
11% to 17% damage.
Aerial normal attacks:
-Aerial Neutral Attack

Dimentio surrounds himself with magic. Quite the aerial attack, this racks up damage quickly and can kill enemies easy if done off of the stage. Since the hitboxes cover his whole body, it's hard to hit him out of it.
15% damage (3*5%).
-Aerial Front Attack

Dimentio creates some magic crystals in front of his palm. It's a powerful attack when it hits right away, but hitting with hit after the crystals stop moving lacks knockback/ damage.
14% damage during the first three frames/ 10% damage afterwards.
-Aerial Down Attack

Dimentio summons a Dimension D square, from which he delivers "an attack 256 times more powerful than normal!". It's pretty slow (even slower than his Front Smash!), but it sends the enemy flying downwards fast!
16% damage, spike.
-Aerial Back Attack

The tricky trickster can even make magic appear behind his feet! This attack is easy to combo into and out of at low percent. It comes out really fast!
8% damage.
-Aerial Up Attack

More sparkly magic. The hitbox cover Dimentio's head, which means the range isn't all that good. However, it can give you some good damage, especially combo'd after an Up Smash or Up Tilt.
15% damage (5*3%, getting all the hits in can be kind of tricky).
Special Attacks:
-B Neutral: D-Bomb (couldn't find good names for the special attacks, sorry)

Dimentio charges up his trademark magic bomb and sends it flying straight on the ground, and in a downwards diagonal in the air. You can charge it up, and cancel the charge by dodging, but if you do so you'll lose the charge. This move is unique in that if you charge it up in the air, it'll make you stop falling and levitate in place!
The D-Bomb moves slowly, but even not charged it deals a good amount of damage and knockback. You can have two of them on the screen at the same time.
12% to 20% damage.
-B Side: D-Warp

A short, teleport-like dash that inflicts some damage. This move has low priority and it's easy to hit or grab Dimentio out of it, so it's better to use if for horizontal recovery - you're not helpless after it and can still attack or double-jump! You can only use it once per jump, though.
5% damage. If you touch the edge of the stage at the end of the move, you'll grab the edge automatically and it will cancel the recovery.
-B Up: D-Teleport

Dimentio uses his famous teleportation technique and can move in eight directions. It causes no damage and you're helpless after it, but it can go really far. The longer you press the B button, the farther you teleport. It has a lengthy recovery upon landing (around half a second).
If you touch the edge of the stage at the end of the move, you'll grab the edge automatically.
-B Down: D-Flip

Dimentio captures his opponent in a Dimension D square that he flips around. It leaves the opponent on the ground. (Think Confusion from Mewtwo in SSBM.) This grab-like attack starts up relatively slow but has good range. Try to surprise your enemies!
3% damage. Some attacks guaranteed afterwards (jab, down tilt, up tilt on big opponents, aerial back attack if your execution is fast enough).
If another player touches the square, he gets zapped and takes 1% damage.
Grabs:
When he grabs an opponent, Dimentio immediately captures him in a Dimension D square.
-Pummel attack:
Fast magic sparks that inflict low damage.
-Front Throw:
The Dimension D square shakes violently left and right before opening up on the side and sending the opponent flying!
-Back Throw:
The Dimension D square shakes violently left and right. Dimentio moves it behind him before it opens up on the side, sending the opponent rolling!
-Up Throw:
The Dimension D square shakes violently up and down, before opening up on the top and sending the opponent right above Dimentio!
-Back Throw:
The Dimension D square slowly gets smaller and smaller, squishing the opponent inside! When it breaks, it leaves the opponent lying on the ground right in front of Dimentio! You can only combo a down tilt afterwards. It's also his most damaging throw!
Miscellaneous attacks:
-Dash Attack
After a small stop, Dimentio splits up into two reflections, one dashing forward and the other backward. Each reflection causes low damage and knockback, before coming back to where Dimentio split up. This was inspired by Kirby's Dash attack while using Mirror powers in Kirby Super Star,
you can check it here to see what it would look like.
-Recovery Attack
When getting up after getting knocked to the ground, Dimentio surrouns his sides with sparkly magic, like in his aerial up attack. Low damage, but it knocks the opponent farther away than you would think.
-Ledge Attack
When getting back on the stage, Dimentio uses a small Dimension D square to attack whoever is in front of him (a bit like his front tilt).
Final Smash: The Ultimate Show!
Snapping his fingers, Dimentio tries to capture all players on screen in Dimension D squares (they can get out of them if they're quick enough). If they get trapped, they can't move anymore! After a laugh, the stage gets dark, and stage lights fall on him and the trapped opponents!
Dimentio snaps his fingers again!
Boom! Five explosions, each inflicting 12% damage! And the fifth one breaks the Dimension D squares, sending the opponent flying vertically!
Ciao!
After that, Dimentio bows before the audience. What a trick!
Other stuff:
-Movement:
Dimentio moves by floating around (àla Mewtwo in SSBM), and his run is pretty fast. His jumps are floaty and cover a lot of distance, and his air manoeuvrability is really good! Only a few characters, like Jigglypuff, can boast having a better air mobility. He'd grab items with his magic too.
-Dodges:
His neutral dodge would simply be him sliding into the background - he's all flat, after all.
For his side dodges, he'd do a silly little flip to the side.
In the air, he'd dodge incoming attacks by quickly flipping from 2D to 3D, much like Mario does in Super Paper Mario. It would look like he's spinning around.
-Taunts:
His first taunt would be 3D flipping, with a laugh.
For his second taunt, he would juggle two magic projectiles and make them spin around each other above his head, before snapping his fingers to make them disappear.
And his last taunt, of course, would be him bowing to the audience, with his trademark
"Ciao!"
-Stage intro and Result screen:
Dimentio would enter the stage by teleporting, and then quickly bowing to the audience. What a crowd pleaser!
On the result screen, if he lost, he would clap for the opponent, with his eternal smile on his face.
If he won, though...
His first victory pose would be to juggle his projectiles while laughing.
In his second one, he would simply bow, say
"Ciao!", and teleport away!
For his third one, the screen would be filled with Dimentio clones! The real one would then snap his fingers while laughing to make the clones disappear, and bow to the audience.
Comments appreciated.