This is the standard ritual magic tech we're working with right now:
[Ritual Magic=4] Collaboration (X MP/TP) - If a caster doesn't want to pay the full MP/TP cost of a spell (either from preference or need), he can enlist other mages who will split the MP cost with him, usually equally but not necessarily. For the purposes of damage or MATK, roll using the stats of the caster with the highest total ritual or relevant magic-school rank. Other casters are essentially functioning as MP batteries/conductors for the more skilled ritualist. Casting time is equal to (MP cost*) - (the leader's ritual ranks) in hours.
*MP cost paid by a single mage. If the MP is not being shared equally, then pick the highest cost a single mage is paying.
One thing that's interesting about Philsys as it stands is that you don't need to have a MAG score to have MP. Technically.
My question is this: Should it be possible to use that MP for something?
Phil suggested a mage could take it using a "rasp" sort of spell, which makes sense. Theoretically you should at least be able to suck some sort of magical resource from a non-mage.
A further question. Should it be possible for a non-mage to assist in a ritual by acting as an MP battery for the group, or is it too implausible that a non-mage participate?