My dad and I have been playing since homecoming has launched (and we played from about 2005 till shutdown off and on) but one thing that we talked about recently is that we would like to see new content come out, which now would be a good time, with a fresh start to kind of revamp the way things are done. You could do it as a expansion like update, maybe this expansion adds onto the existing lore of Paragon City or even takes us to another place in the multiverse, but this could allow new zones to be added and having story lines with each, these story lines can lead up to a zone task force that is meant to be done with 8 people, and then overall throughout said part of expansion you can add trials that are meant to be done with leagues.
Another thought we had was updating the models, These could be toggled in the options so that if your PC cant handle it then you still can play. Right now the models are starting to show their age, don't get me wrong the game looks great and aged well from 2004 but polygons... I understand this is a lot of work and that it might not even be possible with the current tools you are working with. But even an update to the current zones like Atlas got to help make it look newer.
New Archetypes and Powersets, you could do this the way the Kheldians and Arachnos were added and require something to be completed whether its just something from a new Trial or maybe even sticking it onto lvl 50 like they originally were, or even just BAM immediate access, however I believe there would be more fulfillment in unlocking the archetype rather than just given it, maybe its a mission arc that explains some lore for the archetype or whatever, depending on if the archetype is very specific like the Kheldians and Arachnos are. Powersets however could be released without unlocking.
Earlier I mentioned new zones all together and I feel like I could go more in depth, now i'm talking like maybe pumping out 4 or 5 connected zones which is why i feel like a multiverse is a better option that just more zones in Paragon City or they could even be an entirely new city that could lay the groundwork for Homecomings own content, which would be chosen on character creation like Hero, Villains, and Praetorians. the new zones could be meant to level the player up to 50 or could be meant as only endgame content, or both, that is entirely up to you guys.
One thing that I know keeps some people playing MMORPGs other than alts would be collections, maybe add a vanity pet system like WoW has that players can collect (this would require an entirely new menu as we wouldnt want to clutter the players powers and when they do a respec - their trays, first it could be small just like 20 or so vanity pets to collect including the ones that currently are in the game. Mounts arent really a thing in CoH but I guess new forms of travel powers could be collected for the tailor such as a blur trail instead of the cloud under our feet for superspeed.
More Endgame content, right now it feels like, and maybe im just blind to it, but once you hit 50 really all you got to do with that toon besides making an alt would be to find a build that works, get all your enhancements and then doing incarnates which with veteran levels that grind is easier than ever and isnt hard to complete.
Idk if it would be wise to do this but maybe finding more rewards to add to vet levels to entice people to still use them, even some of the options for collections i talked about above could be nice rewards for certain vet levels.
Im sure these wouldnt be everyones cup of tea and thats fine but these are some of the things Id like to see added to the game.