I went with your option B like the following:
Existing acct Recruits new acct 6 then
6 > 7
7 > 8
8 > 9
9 > 10

In this way, you have 5 Linked toons that can party togeather. The down side here is you have to Transfer 4 toons if you don't intend to play 10 forever.
This is what I did, & it works great so far.