Generally they're not litigious about it, but make sure you don't name them identically. Most people name them something similar. Rifleman becomes Musketeer or Gunman, the Centurion become the Hoplite or Legionnaire, etc. Then use 'compatible with Battletech or other 1:285 scale mech games' as keywords to get noticed.

A company will always say that making bootlegs of their products is illegal, especially if they're being sold.

In practice, they probably won't care or do anything about it if it isn't in large volumes.