You can't use the paladin for your team, if you don't want to get the account banned. It's a to big risk if you ask me.

I'm not completly understanding you, but i'd say you have 2 options.

1. Make all accounts on your friend's name and use the paladin in the team.
2. make 5 new accounts on your name and boost with the paladin. Once they're 65 or so you can leave the friends account inactive.

I'd go for option 2. If you boost several teams up, then that's a good way to get rid of the problem that only 4 chars fit in the party where you want 5 to get boosted. It's very advised to use the RAF while you can
I regret it i didn't.

Make sure you've thought through what characters you want on each account. It can be handy to have a 'tank' account, a 'healer' account and 3 dps accounts. That way you'll never have problems missing out a healer or so. But downside is that if you have for example a paladin and a warrior on the tank account, you'll never be able to tank with the warrior and heal with the paladin.