Tonight i will have ten 60s on my #1 account. My fivee accts are linked a>b>c>d>e. I thought about doing what you mentioned, leveling them up to 30 or 31. The problem is that you're stuck with a level 31 on acct five. Then if you level another team to 31 youve got two 31s on five and a 31 on four because you havent yet leveled another 60 on acct five to grant that new 31 on four up to 60. Eventually you'd have something like this:

60 60 60 60 60
60 60 60 60 31
60 60 60 31 31
60 60 31 31 31
60 31 31 31 31

You could probably have even more 60s on acct 1 and or 2 because of the cascading grantable levels. I couldnt figure out a way around this without paying to transfer lots of 60s off acct 1 to the other accts. I have ten 60s on acct one but maybe six on acct five, plus a 31 on acct five because i tried what you mentioned and granted the others in his team up to 60. Now im stuck with a lvl 31 auction house mage.

Having just finished my raf fun, id recommend getiing 5 locks up and parking them around the world to help summon your teams to cut down on travel time the next time around. Yes you can raf summon but only linked accts. Acct one cant summon anybody but acct 2. Having locks makes it easy to summon yourself because their portal thing will keep working after they log out.

Just level several teams up to 60. Then on accts one - four, grant up classes that suck to box but that you might want to try anyway someday (rogues!). I would made sure to have at the very least a druid, paladin, warrior, and priest on every account. I leveled all my teams with a warrior or paladin tank. I ended up with a 60 druid, paladin, warrior, priest, shaman, lock, and dk on all five accts. I have four 60 hunters, mages and rogues on the first four accts. I leveled seven teams to 60, one after another. It gets old but youre under a time constraint you cant extend. I did five locks, then five druids. After that it was all tank/3dps/healer groups. After cataclysm the under-60 elite quest mobs are a joke though so you can do 5x any class now. I kept doing the traditional group comp just for practice and to try pre-bc dungeons which is a complete waste of time if you care about speed.

Sorry for the rambling reply.

TL;DR version - you cant just level to 31. The real power of raf is the 300% xp, not the grantable levels. Use the levels for rogues or missing warriors. You have to level all accts to 60 to have many full teams.