Player 2 character swap, unlock mods possible?

My bf and I played for about 9 hours, Moze and Amara respectively. He wanted to play as Zane instead so we started a new game, him Zane me Fl4k.

I missed my swole arm lady and jumped back into the first game with Zane. I was level 16 and he was level 6. We had just unlocked mods and the 3rd weapon slot. But Zane did not have these unlocked as he was didn’t complete the missions with him and we were just gonna power level him.

Is there a way to change p2 coop character and still unlock mods and addition weapon slots when the p1 character remains the same?

This wasn’t an issue in B2 or the pre sequel because he would swap and change characters constantly only being locked out of things by level not missing missions.