I think it'd be neat if Frontier Defense had a big boss titan to fight at the end of the final wave. Something like the mercs from the campaign, but not as pussy. The only two fun bosses in the campaign were Viper and Slone due to being more gimmicky.
Hell, rather than a titan it could be a bigass dropship or tank.
Or maybe even a bigger one of the dragon things from the first game.
Oh, or perhaps a unique titan with four arms and two weapons or something.
TITANFALL
Luke Cook
Jaxon Rogers
Supposedly those are relics of a concept for a titan with exploding punches and a grappling hook.
Hell, Scorch Prime essentially is that Titan,
Lincoln Hill
I used to do that with a CRT and a vis-a-vis marker in games that didn't have a reticle.