Quite simply, I just want more templates! C2 templates made a man (and a published dev) out of me, so I'd love to see more. I know you've added a couple already to C3, but if you could do even more (maybe even simple start screen and end credit scenes) that'd be awesome.
I think it'd be better to leave that to a user poll, and the top 5 ideas get templates made. I'm just one guy and maybe I'd want something specific to my needs that isn't necessarily the best for the community. I personally think RPG, RTS and other, more complex genres are absent from the template catalog (at least in a realistically implementable format). So, if it were me, I'd say RPG, RTS and tabletop games (like Settlers of Catan).
But I honestly believe a community poll would be more useful in the end, and would make ME just as happy as having MY personal queries answered specifically.
That said, I already gave some ideas regarding UI elements that I think would help players complete a game faster and in a less frustrating way. Things like locally-saved high scores and other stuff are a pain to complete without guidance.
What about third party stuff like Google Play Games and AdSense integration? Templates for these things would mean people wouldn't have to rely so much on third-party templates which then get abandoned as the engine code changes.
Take your pick!
Which templates do you want? We could make some more, but it's not at all clear that they would be what you want.