Ok, I see what you mean, so you just want to keep cycling through the list of support team members alphabetically. Well while there's nothing OOTB that would do that for you automatically, I would imagine that on each group object, you might be able to place a user object/field which would designate who the last member of that team who was assigned a ticket.
Then from there you could display that on the assignment when the group is chosen and that would help for a manual assignment.
If you wanted it to be automatic, I would imagine you would need another calculation on the assignment user object that did a GetNamedObject of the same index + 1 of the latest assigned user on the group object. Assuming your looping through the members of the support group in the same alphabetical order.
This is of course hypothetical but it would be along those lines, and of course would not account for how many tickets that a support group member may already have.