Interesting. I never thought of that. I'll give you points for original thinking, certainly.
If you could just use a cantrip, though, it's likely to be overpowered. You could get 8 folks to aid you, and you'd never fail. I'd recommend either limiting the number of people who can aid (perhaps based on the primary caster's skill ranks, Intelligence mod, or something similar), or require the assisters to spend the same amount of MP as the main spell.
I do, however, have something similar in the modern EOM rules for group ritual spells.