@boldmonkey
I agree, but I don't think one necessarily excludes the other. He could still serve more of a reserve role despite becoming a Great General. It would also mean that half of the GG are somewhat loyal to the throne (MouBu, Tou, him).
I'm guessing the sixth is Shou Hei Kun, since central planning loses its importance when every Great General gets to do as he pleases. It's easy to forget but he isn't just a strategist.
Editor: Houken gonna die next battle?
Author: Just like in history. I'll have him 1vs1 Shin.
Editor: Isn't that too soon for Shin?
Author: It's alright, Shin also dies.
Editor: Uhh...
Author: Then Kyoukai revives him with her magical homicidal girl powers!
Editor: I don't think that's the right...
@Torappu doesn't help that the artist is not very good at drawing mecha fights, they are flopping around like plastic models. A good example is of great mecha combat is Break Blade, fights have a realistic sense of speed and weight while being relatively easy to follow.