Alright Welk. I'm trying out your chunk idea. Is this small enough?

Overload: I VERY much like this idea, and it allows for some very dramatic situations. One example would be a circle of Arcanists working on a spell, then them being taken down one by one while the rest struggle under the increasing burden. The question is how easy it is for an over-burdened caster to release it. I'd say that this should not be an easy task, trying to safely "Step back from" the spell. What other questions do you have about the way Overload ought to work?
I agree this should not be easy. I think of it as something like a group of people picking up a large piece of furniture, and then one by one someone lets go until the remaining people cannot support the weight. To throw off this weight, one must struggle to set it down (dispel it), cut it into manageable bits (lessening the spell), or heave it away (send it to another Ancient, possibly the disrupter). There are a whole lot of eventualities to this that need to be covered. Setting the weight down might be difficult to do without “dropping it”. This would require a backlash and/or a release of an unstable spell as a consequence of “dropping it”. I’m not sure exactly what that would be. Maybe the effect of the spell affects the casters to some degree, such as with Subsumal, they change instead? At the very least, the spell would exhaust the casters, some might even collapse. Cutting a spell into pieces might be to remove elements of the spell to make it “lighter”. Since larger spells would be complex, there would surely be some items one would be able to sacrifice. In this capacity, I’d say it would be a race between figuring out which element to remove and the spell overloading. (It would be more convincing if I had examples but for once I’m at a loss.) Tossing off a spell would most likely not work in many cases (especially the lower the number), and even if accomplished, would exhaust the entire group. It would most definitely be a last ditch effort at solving the problem of an overload before it affected the casters involved. Tossing off also requires a receptor. Perhaps an object could be used as a focus, but I was thinking of singling out a caster to take on the load (possibly even an enemy caster, if conditions were just right). This caster would be “crushed” by the spell.

Generally for large spells it would be common practice to have extra casters for support in case something happens to someone during the process to keep overloads from happening. Such additional casters could be solely for assisting in bearing the load or making less of an energy drain for the other casters when the spell is cast. Caster’s might also form a spell in a certain way to avoid an overload by creating an “emergency pull string” or an element of the spell that when removed would dispel it or make it minimally harmful.

One concern I have in this tangent is the ease in order one can be disrupted from the Cumulative Casting. By this I mean that based on the current specifications, if I were to say, knock out a few people, they easily are removed from the casting and will not suffer the eventual penalties should the spell fail. That means if a spell was failing, I could knock out someone I cared about to save them while the others would suffer even greater. Additionally, one with mental magic might be able to enter a caster’s mind while casting and disrupt the spell. So maybe the extra casters would be “shielding” the group from this act.

This whole idea needs a few rules in place in order to be more…digestible. I currently feel I’ve bitten off a mouthful and I’m gagging on the excess. This should also take into account that some casters will be able to bear more weight than others, and that some spells would likely be more unstable than others.