I think the closest you can get to what you wanted is:

main->b
b->c
b->d
b->e

(boost b,c,d,e with main - gift all levels to chars on b and re-gift onto main (plus the actual earned grant levels), transferring as needed



Or if you really wanted to use the original 6 accounts:

main->a
a->b
b->c
b->d
b->e

Then you could re-gift from b to a, and then again from a to main

EDIT: ( Or you could do what you just wrote while i was posting this )