What about an onion of a game? You know, peel back the layers until you have something manageable/not overripe?
Outer layer: magic/metaphysical combat+. Who wants to see 4+ players A) choosing spells each round, or B) trying to figure out how to maintain their prior spells, get defensive against the enemy tanks/chargers, and still have enough actions to cast a 2nd level spell from a spell implement? Peel it off.
Next layer: combat. Each PC's armor reduces incoming physical damage by a fixed amount (which is a simplification of that armor's protection die). PCs aren't fixed to a grid, but the GM can add a defensive posture to character positioning, and all those PCs might then have flanking options too, which is a juicy but thick layer of onion. Peel it off.
Middle layer: extended conflict. The reason combat is above this layer is that this lays the foundation for combat: turns, actions, and making progress toward a goal. This is a
maybe layer for big groups; it allows for team members to contribute to a common goal without over-complexity ("does my shield provide protection? Wait, I need an action to use it?"). Peel it off, but set it to the side, just in case.
Next layer: characters. The building blocks of the actors in the game. You can tinker with this layer (slice, dice, or mince), but it's essential unless you're going for the simplest of RPGs. Keep it.
Onion core: the basics. What's a roll? Why is it called a contest? Do contests get more difficult? The core of the onion takes it from role-playing to role-playing game. Keep it.
One more thing about this onion: if you have toothpicks, you can add decorations, Mr. Potato Head-style. I call them rules modules. For a big group, you might alter the Round (202), Turn (203), Initiative Contest (212), and the Reaction (214) rules to allow for a group-discussion-style round of conflict, or a regimented use-all-your-actions-quickly type of round. Whatever you think will work best.
Start cutting onions and get teary-eyed here (rules under "Five Rules Modules"):
Modos 2 is the second edition of the light, modular, role-playing game: Modos RPG. It is a tabletop RPG for two or more players, with one player guiding the rule
modos-rpg.obsidianportal.com