You could start by posting the changes on the forum, some of the modders would then put it on the SVN if they agree with the suggested change.
Eventually you may be granted SVN write access. I think Thunderbrd is the one you should talk to about that.
I find it odd if it really works with that change.
examples of events that does not have <UnitsRequired> defined, and have <iNumUnits> X>0 </iNumUnits> that seems to work:
EVENTTRIGGER_STUCK_IN_SWAMP
EVENTTRIGGER_QUICKSAND
EVENTTRIGGER_TARPIT
Test it out for a while, confirm that the event still happens for ships at sea, that it doesn't happen on plots with no owned units, and that it never happens on land.