If it were within my power to buy the IP for COH this is what I'd do:
I would NOT bring back COH as we knew it.
What I'd do is hire back every dev I could from the Paragon Studios team and have them rebuild COH from the ground up as a sequel. Same gameplay we all know and love, same aesthetic but more modern tech/graphics and way better coding. Basically picture COH with a new coat of paint even more options and far more optimized code. Every costume piece would be recreated for the new engine. We'd all be able to recreate our costumes exactly as they were but we'd have a ton of new options on top of it.
The reason why I'd do this instead of just firing up the old COH is because the old COH is just that... old. It's not enough to just bring back the old faithfuls. I'd want a new COH to not just survive but thrive! As a new game with newer graphics but all the gameplay/story arcs/features we loved plus MORE content on top of it, a new COH would not only bring back the old guard but potentially ignite interest from new people as well. I'd ensure the base builder was overhauled and updated but still capable of doing all it did and more. I'd also ensure all the code was clean and thoroughly documented
Two things I'd do that I think the community would appreciate include:
a) Get all the old account info from NCSoft in the deal to buy the IP so I can offer returning players who invested in COH all the unlocks they previously had before the original game went down. So if you had all the AT's/Powersets unlocked at the end you'd start the new COH with all that stuff unlocked too. It would be my nod to those loyal to the original game.
b) I'd make sure the client could be easily turned into a stand alone/lan based game in the event of a future shutdown. Basically if I was unable to keep the game going I'd make sure people could take it with them.
What I wouldn't do:
I wouldn't give anyone remade characters from the old game. Everyone would start off from scratch, albeit with unlocks they had previously.
This is something I daydream about often /sigh