Well lets see what you come up with. Seems still that with multiple characters per account mine would still be the best, although you would level them up in sets of whatever number of accounts you have.

So say you have 10 accounts. You level up 10 level 80's by leveling all to level 40 and then just two to level 80 and doing one trasfer (at this point there is almost nothing left to grant).

Then do the same for another set.

I would be surprised if there was a better way.