Much as I hate to say it, I think the only way to draw big(ger) numbers to AH is going to be as follows:
1. Come out with a MouseJoy option that makes it playable for people who not only don't have joysticks, but wouldn't know what to do with them if they did. (Not Arcade WT, but "Realistic" <--- I use the term loosely)
Basically this means taking combat trim to the next level for mouse users... Honestly, with how Aces models gun dispersion, I think this could be MORE successful an implementation than WT (In WT, MouseJoy lets you throw 37mm rounds like laser beams). People WILL squeak, however, when the 5-10% of skilled players using mice start beating them. That's inevitable.
2. Come out with some sort of F2P option for AH. Limited Plane Set? Other limits? I dunno. But having tons of planes in the air flying for free is going to draw the people who will pay, if it's done right.
You aren't going to skim off the tiny sim groups in games like IL2 (CLoD or BoS), WT Sim-mode players, etc, simply because they aren't going to get past the graphics/interface to give Aces High a chance... Even if you could perfectly showcase the beauty of the big arena, or how kickass FSO is, the pond of players equipped to jump right in and fly a game like Aces just isn't that deep anymore.
Bottom line is, in order for Aces to grow again, things are going to have to change... and when your current apple cart's contents are 80% fragile snowflakes that melt-down over minor things... well, I don't envy the team that has to sit down around that table and make those decisions hahaha