An aside – How do requisites affect which spells can be affected by magic?
A question raised during the forum discussion asked if a Muto Vim effect could change a spell enough to make it no longer effected by a Perdo Vim form specific effect. e.g. A Sun duration Rego Terram effect is altered to a Rego Aquam effect at cast time – can a Perdo Vim/Terram spell affect it if it has “changed” the form it uses? Further could the same Perdo Vim spell affect only Terram spells, or can it also affect spells with a Terram Requisite?
I tend toward thinking a spell with a Tech and two Forms can be affected by either Form specific dispel effect. The unraveling affects part of the spells structure and it doesn’t really matter which form it unravels to make the spell loose it’s cohesion. This makes requisites a slight disadvantage, and implies that some part of the original spell is still there to be unraveled.
But I hold the same concept to other ways of affecting spells it also introduces an advantage to Mu effects affecting the Forms too. i.e. a Muto Vim Terram spell to alter Range up by 1 mag can be applied to any spell using Terram, either as the base form or a requisite. I don’t see adding breadth of application into Vim spells as unbalancing.