Last time I was into BTB was H3 and it was because of the amazing maps that I played. Playing regular 4v4 on the larger maps felt empty, but the 8v8 was perfect. Honestly, I am fine with them putting more time on it, but I was very impressed with Warzone when it first came out. I liked that 343 took a chance and developed their own game type that basically was an industry first, and very much Halo-like.
I would like to see them launch with classic halo types like: BTB, SWAT, team doubles, infection, griffball, and slayer. All with good maps for each, but that's almost impossible.
A new game type like a Halo battle royale would be pretty cool honestly. When this game finally comes out though BR may be overplayed (if it isn't already).