I would personally take the account with the single highest tank type on it.
And not RAF from that one.

Or if you want a bunch of RAF'd toons on that account, consider a character transfer.
With the tanking type moved to the account which will not be linked.

Then use the tank type to boost the other four.
And get a whole slug of toons at 60th during the RAF.

If your set up is similar to this:
A
B - D
C - E

You can level toons to 60th on BCDE twice, and then grant toons to 60th on BC once.
Which gets you BC x3 Toons at 60th and DE x2 Toons at 60th.