What would I change... oh the list goes on and on.
Eliminate TOs/DOs/SOs, replace with enhancements that are functionally identical to standard IOs: Because who uses standard IOs, and who uses TOs/DOs/SOs when they have access to IOs, or IO sets? The old TO/DO/SO system is kinda depreciated, and also annoying in that your enhancements can totally shut off when you gain a level, actually leaving you weaker for levelling up. This would stop that crap from happening.
Crab Spiders can Wear a Cape: 'nuff said, basically. I hated the fact that taking even a single crab spider power in any of my alternate builds kept me from using the Bane Spider backpack that sported a cape. C'mon, gimme a caped crab-pack - Lord Recluse wears one! (well, kinda...)
Crab Spider Suppression gets buffed: I always hated the fact that Suppression, which basically represents a wall of spastic Channelgun firing, and is the signature ranged attack of a Crab Spider, was so much weaker on a per-hit basis than Channelgun itself. While I wouldn't buff the damage to the point where each tick of Suppression was equal to a Channelgun shot, I'd certainly make the damage roughly on par with a Longfang tick.
The ability to mix AT-specific and generic costume parts: I was always miffed that I couldn't wear any parts from my AT costume as an Arachnos Soldier or Widow in my basic outfit, with the exception of required AT-specific parts, like the crab pack, assault rifle, and claws. I would love to wear a Crab Spider helmet 24-7.
Eliminate all involvement from NCSoft: NCsoft's screwed me over one too many times. I would rather have any company, with the possible exceptions of Ubisoft and EA, running CoH instead.
Allow for Offline Play: Your single-player and multiplayer characters would probably have to be kept separate, but being able to play singleplayer when the servers are down would be great. It would also provide excellent 'insurance' in the event of a game shutdown.
Allow for personal servers: Move the game over to a Buy-to-Play model like GW2 is using, and grant the user a server-license in addition to their game license, as well as some basic (but functional!) multiplayer server software. This way, players can host their own servers, and the game's company doesn't have to host a metric ton. They can let the playerbase do that. being able to host their own servers would also provide yet more 'insurance' in the event the game gets shut down for good. The official server would close, but playermade servers would still work just fine.
Voiced Cutscenes, and more emote animations for characters to use in them: I would love to hear villains' diabolical monologues and heroes' pithy one-liners during cutscenes.
Costume Unlocks Revamped: Just about every costume option available should be earnable ingame, without cash-shop BS. You can unlock them via the cash shop and save yourself a grind, but if you want to earn it, you can. New costume options/packs would be released in the cash shop ~3 months before they're available ingame, allowing the fashion-conscious to ride the latest trends while those more frugal will wait for the ability to earn it to open up. All costume unlocks, without exception, will be accountwide.
Unlocking new powersets: Every powerset that's locked off by default should be earnable in-game, perhaps via a task-force style epic story arc, possibly coupled with a merit grind of some kind to unlock the ability to take the story arc. You could pay the cash shop to unlock it immediately, but if you wanted to earn it, you could.
No merit or inspiration restrictions on free accounts: C'mon, free players can't even earn merits? Or any inspirations except small ones? That's BS. I can understand keeping vet costume parts and vet powers locked behind subscription, but insps of all sizes and merits should still be earnable.
Long-term free accounts in good standing recieve whisper/mail privileges: The biggest reason why free accounts got their whisper/mail privileges locked was because of spammers. If an account goes several months without any infractions, and the account has clearly been played regularly during this time, the whisper/mail restriction should be lifted.