I bought the game (beta linux) and I'm looking forward to seeing a lot of people playing, I think you could add some new features to popularize the game.
Support Oculus rift: source engine already supports the device.
Support Razer Hydra and Sixense Stem (new razer hydra wireless)http://www.youtube.com/watch?v=MH3v2VrCZ9Q#t=0
You could turn the game on free to play and make money from micro transactions, follow the example of team fortress 2 and other games that got paid and then became F2P. (Who bought the game wins a special item)
Add the option to create a WAN server at own game menu, reducing the reliance on dedicated servers (the game options I only saw the possibility of creating a LAN server)
I live in Brazil and all the servers in Europe and the U.S. have very high ping here, with the possibility of the people themselves to set up a WAN server, me or anybody here in Brazil could be the server and thus have a much lower latency!
And with Linux support you guys are developing, I think you guys have good plans for the SteamOS and Steam Controller, which can greatly help you game