I would probably go with a chain like this:

A -- B -- C
A -- D -- E

And then character transfer a boosting toon to the "A" account.
And boost several sets (ideally 4 toons), on BCDE with A.

Every four toons boosted (four per account, on BCDE), gets you:
- Four toons on BCDE.
- Two toons on BD from CE, via granted levels.
- Four toons on A from BD, via granted levels.
- Two additional toons on A, from BD based on granted levels received from CE.

For a total of:
A) Six plus booster.
B/D) Six.
C/E) Four.

That gets you, whatever you want to add to your existing five toons for PvE and for PvP, and possibly another set or two, of something you'd like to try but did not level up on your initial five.
Chances are, you are primarily interested in PvE or PvP, so from 60th level the five which will help you the most first.

You can RAF to 60th in a couple of days, fairly easily.. say a weekend. Or a week per team, playing rather casually.

If you're doing another five accounts from scratch, I'd definitely RAF and get a few toons.