If you make a F2P 10 twink I don't believe u can line up for bg's or arena.
I made a few F2P's, locked their XP at 10 and geared them up then unlocked the XP and then bg'd to level them. In my footer you can click a link to upcoming F2P's. They are lvl 17 atm. Was fun doing it though. I will do it again next time I make a F2P but atm I'm having too much fun with 20-29 bg pops
Oh and incase ur wondering, I did lock them again at 15 to gear again via dungeons. Then unlocked to keep bg'ing.
We actually tried to do this back in MoP to farm heirlooms early on. There were a few people on Aerie Peak iirc that actually stuck with it for awhile.