MKF30 Yeah, one of my favorite things about this game is how even if the moves are similar, they are never the same visually or in properties. Or at least in some distinguishable way. It's really cool how they did this, making each of the characters go from clones of each other, to completely different. SF does change things up, but not to MK's extent.
Sixoul I think that is once again more opinion. On the team thing I mean First, just my opinion, but time should always be really long, I hate time outs, but I don't know. Now, on SG that could work, but the thing they are doing is untested, never done before, so it's not completely certain how it will work. I believe it will do wondrously, but who knows? Team games are usually looked down upon though. They can be done really well, but it's a bit difficult to do it properly, and can blur the line between gimmick and depth
Again, if you want to do teams and how you want to do it (share a lifebar, one dies the other loses, all have separate lifebars, etc.) that's on you and how you want your game to work. Reason MK9 tag doesn't happen a lot is because it's a bit glitchy and there are a couple infinites and whatnot. :/
Finally special moves? When I want to make a special move, I literally just think of what would look really super cool (I watched a lot of old kung fu movies and stuff, heh) and mess with it, try and make it viable and balanced for a character's moveset. It'd be hard to gather every type...
Charge style attacks
retreating techniques
Anti air grabs/hits/projectiles
Izuna Drop (the ninja piledriver)
Tetsu-Zanku slamming them with your back. Kinda like Yun)
Dive kicks
dash punches
reflects (projectiles)
Counters
flight
invisibility
The list goes on...
Check out Mortal Kombat Armageddon, it was not that great of a fighter, but it had an insane amount of characters, therefore insane amount of special moves.