I'd definitely be all for a Grandus Titan. However, remember this is Titan *class*
I like to think that each year we get a Titan Class toy it is special (hopefully like the Commander Class will be in time, 2 years in a row is good, but not enough to establish a pattern yet).
I know a lot of younger fans are enamored with Armada Tidal Wave. He would make a great CC figure, but not a Titan Class.
Aside from Grandus, I'd definitely be happy with Raiden (6 voyagers just like CW/UW Devastator), or even Monstructor/Dinoking at that same 18 inch scale. I'm going back and forth with Galaxy Shuttle. He certainly is big enough, but never really did anything in Victory worthy of his size, which was kind of sad.
Repaints such as Black Zarak and Metrotitan would be welcome, but I think those would be more for a

Selects release.
Although Fort Max reused many of T30's Metroplex' parts, it seems the past few years Hasbro has wanted to make each Titan Class toy special, lets hope that continues for years to come. Would I want a more *Original Series* looking Metroplex?, perhaps in time, but I'd rather have every truly obscure character worthy of a Titan Class figure be done fist, before Hasbro starts doing them again.
Bucket/Want List: Botcon 2016 Customization Class Ratchet (G2 Deco), or Customization Class Ratchet (Marvel Comics Deco) **would also be willing to pay for an Unpainted Botcon 2016 Ratchet, TT Legends Fortress Head (only) with working Electronics
Wish List of Modern Combiners: Road Caesar, Monstructor & Dinoking (proper size to fiction), Landcross, Guard City, Battle Gaia, & G2 Defensor. Wish List of Titans:Metrotitan,Majin Zarak