I completely forgot to mention Jigglypuff when I made my post, last night! I assume due to her basic round shape (and, I guess, that Kirby is waay cooler? xD), there are very few actual vertex hacks of Jigglypuff. If you do a quick search in the vault you will find that she only has 19 total hacks that are labeled as vertex modifications. If you exclude model imports/swaps, texture hacks of pre-existing vertexs/imported models, and revamps, Jiggs has a grand total of 8 vertex hacks, which places her above King Dedede on the list of least vertex hacked characters. Additionally, if you remove the hat only vertex edits from Jigglypuff's pile, she's reduced to only 2 vertexes, total, which puts her at either tied with Mr Game & Watch or in front of him for #1 spot on the list, if you don't count making his dash attack helmet always visible a legitimate vertex hack.
Now, I'm no vertex hacker so I don't know the facts, but as I implied previously I assume that Jigglypuff's minimalistic shape severely restricts what she can be stretched into. Keeping in mind that I've made this assumption, here are some ideas for her:
Igglybuff (Jigglypuff's pre-evolved form)Wigglytuff (Jigglypuff's evolved form)HoppipClefairyVenonatTogepiI'm sure there are tons of other Pokemon that would also work well, but my god, there are a lot of those things...
If I am to pick a single Pokemon of those above to be my suggestion, I pick Hoppip. I choose Hoppip because it'd be the most significant/impressive/challenging change to Jigglypuff's model and Jigglypuff's 5 jump floaty moveset will still make sense (though side special will be awkward). Clefairy would be my second choice for similar reasons to a lesser degree.
For non-pokemon suggestions, I have no ideas. I'll let you know if anything pops into my head, later.
EDIT:
How many ice climbers vertex are there?
My slots are filled up with StarWaffle's Moss Climbers, Autumn Climbers, Sand Climbers, Water Climbers, and "Real" Ice Climbers, which are all texture hacks with vertexed weapons and (maybe?) minor model edits elsewhere. Additionally, there are Lemmings by Virt V9 and StarWaffle's Hammer Bros.
Also, thanks for the high-fives earlier, guys

EDIT2: And yes, Vegeta may not be my kind of Brawl character, but I must say, he
is looking mighty impressive.