Fighting multiple opponents is enough of a mess as it is, with at least three different approaches in use across the range. I'd rather have the current muddle made clearer than start slinging in new complications.
I have created something interesting to cope with this. Say fighting with multiple enemies.
First things we should ask:
How manny of them? In my system you can be surrounded max by 4 foes with human size.
Next question: how big they are? 6 of them max if they are small like goblins or dwarfs. 3 for the big ones like trolls.
You get skill penalty of -1 for each opponent you fight beyonds the first. So you get skill reduction of -1 ,fighting 2, -2 for 3 and -3 for 4. In case they are human size.
More to add: strategical positioning when fighting numbers inside a room, cave or narrow pathways.
For example: with the back on a wall you reduce the max number of foes to 3 instead 4. With the back to a corner of 2 walls you reduce to 2, like 2 friends fighting covering backs each one gets 2, and corridors max for 1 obviously.
My mini system focus a lot on the micro aspects of battles, class skills, spells, positioning, while remaining simple and comprehensive like good old FF should be, and satistfying cause gives you more freedom to act and combo some specific skills.
Lot of strategic use of skill lets say.
I wish i could share and help.