The feature was dropped due to networking constraints
Marvel vs. Capcom 3 is well known for its zany and over the top gameplay, so you can imagine the chaos that would have ensued if the developers of the game were able to make it so that 6 players could play the game at one time online.
If you played Marvel vs. Capcom 3 online, you’ll understand all too well how bad the online netcode was at that time, as this was in an era before developers regularly implemented rollback networking.
Having 6 players all online at one time in a single match, each controlling their own character, would have made for some spectacular moments, but it wasn’t meant to be back in 2010.
Fast forward a few years later, and Street Fighter X Tekken was able to implement a Scramble Mode into the game, where four players all played at one time on screen. Clearly if this was possible back in 2012, it’s a feature that Capcom could potentially roll out in a new Marvel vs. Capcom game.
2XKO, the upcoming fighting game from Riot Games, also features a four player mode, with each competitor taking the controls for a single fighter. This will work with the core gameplay of 2XKO, as the point person will control the action until they tag in another character, at which point the other player will take over.
While this isn’t four players on screen at once, it’s a standard feature in 2XKO for four people to be able to play the game together, with two competitors taking turns at one time.
If the next Marvel vs. Capcom game is a 3v3 fighter, you could see a similar system working as part of the core gameplay, with teams being made up of three people facing off against another three competitors, with just two players on screen at one time.
However, it might be fun to include a Scramble Mode where there are 6 people on screen at once. While this likely wouldn’t be balanced in any sort of way, it might be a very fun mode to explore and see what’s possible.
It wouldn’t be the first time the creators of the Capcom Versus series threw balance out the window and created a fun mode for players to enjoy for heavily outside the box gameplay.
Source: Event Hubs