Moyreau says:
Hey, by the way, Vicky, I really don't want to handicap you too much, but I really think that casting a spell on multiple persons should either use the Multiple Targets/Area Effect perks, or have the Endurance cost be cumulative (on the Spell Endurance chart, E. g. casting a +1 spell on 2 persons should be the same as casting a +2 spell, or 2 Endurance); whichever is cheaper.
Does this only apply if the repeated castings are all of the
same spell (e.g. multiple levitations), are are you suggesting to make it cumulative based on the total of all the abilities maintained simultaneously (on self and others)? I'm asking because the choice will significantly shape how magic works, what is and isn't workable &c. (It's important to ensure we're on the same page about how this works and how it does not, otherwise I'll make wrong conclusions and also probably occasionally declaring impossible actions.)