Hmm... I like me some DOA2U, though at this point I think that its movesets might be a little too limited. DOA4 (and DOA5) expanded the movesets a fair bit. If a DOA4 Remake had some cleaned up mechanics moreso in the vein of DOA5, it could be an outstanding game.
Later doa's didn't have more in a practical sense...we always have the same characters that are represented. You have the lolicons with Marie and Honoka, us ninja players, Christies, Jann Lee, and a few Kokos, Hitomis and the eww 2D characters, if female
Just putting into perspective that DOA5LR (36 characters) & DOA6 (31 characters) have a lot more characters than a game like DOA2U or DOA3. Although, on the other hand I was fine with VF5FS's roster and it only had about 19 characters. I think DOA4 was the first DOA to break 20 characters and one thing I liked about that game was how it expanded a lot of character's movesets compared to DOA3 or DOA2.