Re-query the abilities of the proxy
Currently once you've added a proxy it does some initial discovery to decide what it manages. If you need to change that (say to remove dhcp management) you have to remove the entire proxy and readd it to make Puppet aware those roles have changed. This can be a pain and it would be nice to issue some kind of rediscover command that checked all the proxies for current roles. Or they reported in every so often, whatever works.