I don’t mean actually setting up predetermined combos, I mean a game mode where the game just sits the player down and teaches them the mechanics of a combo system so the player will have a better way of discovering combos for themselves later on.
This is distinguished from challenge mode combos or trial mode combos in that the game isn’t explicitly telling the player what combo to do, rather, the theory behind why the combo works the way it does and how combos are discovered and formed. An in-game tutorial could exist explaining all the combo limitations in UMvC3, SFIV, BB, GG, whatever, but it doesn’t. The systems themselves don’t need to be simplified, they just need to be explained better.
Like for an example, take GGXXAC Jam. The game would first show the player that you can gatling 5K, 5S, 5HS, 6HS HS. Pretty simple stuff, and lets the player get a feel for gatlings. The game would then move on to show that you can do 6HS, 6P, 5HS as an example of a link and a gatling put together. Then the game would pause, and ask the player to put two and two together and have them work out an extended combo. Then the game would go on and show the player the power of 236S-D and the wall stick it provides, perhaps showing the player that they can run up and do 2S, 2HS, 6HS HS, and then ask the player to think of additional followups to the wall stick, or different ways to get the wall stick in the first place. The purpose of this mode not being to teach combos per se, but to teach how to approach a game’s combo system and how to create new ones.
Oh, and the shoryuken invincibility thing is done in Arcsys games with the little white circles showing up if you hit someone while they’re invulnerable. It’s not a perfect way of telling if something is invincible or not due to all the stuff that tends to fly around the screen, and the way the background flashes and changes color wildly during supers, but it’s an attempt at the very least. The exclamation points that show up indicating high/low blocks are also nifty additions, and the double exclamation indicating unblockable is great in P4:A. The exclams themselves won’t fit the aesthetic for all games (they’d be quite jarring in SFIV), but it works pretty well for the games that they are in.
Regarding execution, fighting games have gotten rid of all the actually difficult motions to the point where simplifying them any further would pretty much be the complete removal of them, which has ramifications on the competitiveness of the game itself. It may be possible to remove them altogether and still maintain a competitive game, but that’s unexplored territory as no game has seriously tried to do that and all current games are designed with inputs in mind for balancing purposes. P4:A tried with 1-button DPs, and only QCF and charge motions, and the game isn’t bad at all. Could use more buttons though, as there are a lot of button combinations for universal options.