Question about porting out a number, while keeping AAL promo

My simple choice NAFUTT4 account is maxed out at 10 lines, the majority of them being free AAL lines.

One of my friends with a free line needs to leave my plan and get their own separate plan, while keeping their phone number. I’m well over a year out from making any changes to my account, so deleting a line shouldn’t affect any applied promos.

Is there a way I can port that number out, while still keeping that free line?

Can I tell tmobile “hey, change the billing on (additional $20/mo) line X, so that it’s a free AAL… but bill the $20/mo to the current free AAL line Y”, and then port out line Y? that would save me $20/mo.