I like:
A > B > C
A > D > E

You can boost with A.
As both B > C and D > E are valid RAF chains.

You can also level a 5-man team, of all new toons, across ABCDE.

It you do boost, the dual chains get you as many (or more, if you boost 4+ sets) granted toons on A, as the number of sets boosted by A on BCDE.