[FE7, FE8] How to enable support bonuses during Arena battles?

I realize this is a bit of a strange pursuit, given that it’s kind of the opposite of what many ROM hackers seek to do, but even so…

FE3 and FE6 (and possibly FE5 as well, though I never got far enough in that game to see) both allow a unit to receive support bonuses during Arena fights. FE7 and onward disabled this, but I’m curious about how one might go about adding that feature back into FEs 7 and 8?

Any help is appreciated!