Welcome to Librarium Online!
I recently got into a beta test for an online game that could very well appeal to 40k players. It is a time limited turn based strategy game pitting players against eachother. You can build an army, customize it with modifications, drop it on a planet, fight other players, use "command" powers to tip the scales, and if you win, salvage your enemies units for your own army. While it lacks the intricacies of a good game of 40k or Fantasy battle, A full battle from deployment to cleanup can take as little as half an hour.
If you're interested, drop by www.tinywarz.com and fill out a beta application.