The actual game is merchandise. But the designs are not, am I right? So whats to stop some one from making an "inspired" design of a Tomahawk? If you guys played MW4 , you'll notice that one of the standard mechs is actually a design inspired by a Destroid Phalanx, called the Longbow. And yet, HQ did nothing at all about it. The reason why they didnt do anything is because the Longbow isnt the same design as the Phalanx.
Frankly, Id rather that Battletech not use any Macross designs. Macross designs are more streamlined, and Battletech is more utilitarian.