The thing about tag fighters that has always puzzled me is when you're able to tag. Now, Capcom and SNK have had a pretty strong lead in that genre so part of the problem is that most tag fighters involve links rather than gatling/revolver action combos, and links offer extremely poor feedback because nothing comes out at all if the timing is wrong, so it'll be interesting to see how much control they give you over tag combos.
Also sometimes there are mechanics like Dengeki Bunko Fighting Climax's trump card system, where you spend one of the tokens that are required to burst on a mini-super that also puts you into a special state, so that you can call in your assist even during active frames.
But yeah, hopefully Heart from Arcana Heart gets added to the game because ASW publishes that series in Japan as well. This is also a good opportunity to get some preliminary sprite work done for Persona 5 Arena if they decide to keep it as a sprite-based game (my theory though, is that with Dancing Star Night and Persona 5 the Animation airing in Spring 2018, that we may get an Unreal Engine P5A announcement at the end of the season, or possibly between cours.)