Some years ago, there was a total conversion Mechwarrior Combined Arms mod for Crysis Wars.
Then PGI/MWO came along and strongarmed them into stopping developement, because that free mod was better than their pay to win game.
Now there is a new version, made by some of the people from way back when!
If you want a really fun Mechwarrior experience and NOT want to play MWO, then give this a look see:
https://clanjadewolf.net/mwll/
There you will find a .torrent with both Crysis Wars and the Mod in it.
Which should make installing and starting it easy. And yes, that is legal.