We use a SP to block a list of Countries, but recently need to allow certain IP's in one of the blocked countries.
I also have later SP's that need to execute to allow WAF modifications.
If I could have country allow/blocks in a custom SP, then I could add the allowed IP's in an earlier rule, then use the Next Policy action to bypass the subsequent rules (the country block rule), and subsequent Service Policies would be processed.

With the current SP definitions, this cannot be done without bypassing all further SP's.