[p4] Branch rename question

[Smith, Jeff]

We have a situation that requires us to rename a branch and then use the
old name for a new branch.  No comments on ways to avoid this are
necessary :-)  We are aware of what has led to this and are taking steps
to avoid it in the future.
 
What I would like is any experiences solving this problem.  The best
solution is one which makes looking through history and performing
future integrations as clean as possible.
 
Problem: Given 2 branches (BR1 and BR2), we need BR2 renamed to BR3 and
BR1 branched to create a new BR2.  Note that the existing BR2 was
created from BR1 at some point in the past.
 
Solution 1:
integrate BR2->B3
integrate BR1->BR2 (accepting source)
 
Solution 2:
integrate BR2->B3
delete BR2
integrate BR1->BR2
 
Solution 3:
integrate BR2->B3
obliterate BR2
integrate BR1->BR2
 
Solution 4:
use checkpoint surgery to rename BR2->BR3
integrate BR1->BR2
 
It looks like solution 4 is the cleanest but also the most risky.  I am
interested in comments from anyone who has been through a similar
exercise and their experiences with any solutions they've used.
 
Thanks,
Jeff