I always figured Guyver would work in a few ways in a game...
- Hack and slash game - Like Dynasty Warriors or like Transformers: Devastation ( also by Platinum Games). I say TF:D simply because there is less overall enemies on screen, which would be a bit more accurate to the way the Guyver fights. 2-3 Zoanoids at a time, rather than 5-10+ like in Dynasty Warriors games.
- Turn based Strategy RPG - Like Super Robot Wars, Shining Force and others. While Guyver may not be quite big enough for it's own game, it would be cool to see it including in a game with other like series. But it's a great way to have a lot of different enemies, without worrying about scale and such. Would make using thing like the Draglord and Gigantic Exceed even easier.
I think essentially, as long as normal enemy units died fairly easily, since the Guyvers can really tear through normal Zoanoids easily, and a lot of Hypers still don't give them much trouble... I would be mostly ok with it.