Increasing the limit of the number of particpants in the free H2H games might not actually be too bad. Maybe up to 10~12 is good.
A lot of people would only think of playing for free, but among those people many new players might be interested deeply in a great game where you can play 10~12 player games for free, and might wish to get a paid subscription and find out more about the regular arenas.
As the potential of HTC and AH grows, I believe the quality of generous free services can also afford to grow with it.
However, I agree that current H2H player game is, considering that they are totally free, just about "more than enough" to the non-paying fans. I've been in simular multiplayer games in IL-2, and I have to admit despite the superior graphics and some interesting modelling features, AH still offers a far superior and user-friendly, fun MP conditions than IL-2 for totally free. That's an incredibly generous gesture in part of HTC.