Here you go tell me what you think.

Under the current rules a regent may not invade more than one domain at a
time with a declaration of war. Below is an action that will cover this:

Declare Multiple Wars
Type: Domain, Free
Success: Special
Cost: Special

During the war planning a regent may decide that it is to their advantage to
invade more than one domain at a time. In order to do so a regent must use a
domain action to delcare mutilple war against the target domains. Doing so
costs the regent no gold bars but only a domain action. The standing rules
for the declaration of war action are then used.

When a regent has declared war or multiple war against target domains and
during the course of the beginning war moves, an ally of the agressor is
attacked the aggressor may be able to counter attack the new threat using
this declare multiple war action. In order to do so the two nations in
question must have a formal diplomatic alliance that involves a defense pact
of some sort. When this condition has been met the agressor domain, already
at war, may invoke the declare multiple war action as a free action if they
still have a free action remaining in the action round. Using the this
action after the regent has already used the standard declare war domain
action cost one gold bar and 1 regency point per addtional domain war is
declared against.

Let me know what you think.