Changing Business Unit Organisation & Avoiding Reassigning Roles

Hi all,
I was wondering if anyone had a tip for the following problem encountered
in 
CRM 3.0.
Our Business Unit organisation changes from time to time (to stay in line 
with the Sales organigramme). Each time we move a child Business Unit from

one parent Business Unit to another, the user roles are lost. Is there any

way around this?
I suspect that you're going to say no, but I figured I'd ask before the 
changes we've got to do this week on the off chance I'd be wrong...

Many thanks in advance,
Christopher
-- 
Christopher Grove