If you are confident with your shell scripting and command line, you can use bpdbjobs to list out jobs and cancel or suspend them.
Say you have backups running and you want to kill them all at 11:00, and start one particular policy.
1. have crontab run your script at 10:55 to deactivate all active policies - so no new backups can start
2. after deactivation, continue your script and kill active jobs
3. have your script activate only the policy you want to start
4 wait, then reactivate the rest of your policies.
If you are on solaris or linux, this is farly easy to do.