Hmmm... you do know about Heavy Metal L-Gaim as well as Nagano's works in Z Gundam and Gundam ZZ too, right?
But anyways, probably my favorite FSS design as of now would be the Junchoon and the Engage SR-3, mainly because they are based on another favorite design of mine - the eponymous L-Gaim Mk I of L-Gaim.
My god man, I have no idea what this is, but it's more legendary lighting from you yet again. *_* That big ominous thing totally looks believable. The only thing I'd note is that the legs look slightly flatter than the oh-so-3D scales of the upper body. Lovely composition.