adzling, that argument is inherently fallacious. "Using 8 spirits in a single combat is inherently broken, therefore being able to bind up to your charisma # spirits is wrong" (Not sure if that's the Slippery Slope fallacy, the False Dilemma fallacy, or some other one)
Kiir I appreciate your dedication to logic!
My Logical Form statement would actually look like this:
If you have 4-8 undetectable, powerful allies that can do almost anything, that you can take anywhere, regardless of security, and summon without any way for someone to stop you (mage cuffs and other methods that stop casting or astral perception won't work)
then you render the entire concept of a team, which is the core of srun play, irrelevant.
Shadowrun is a team game.
Therefore Binding limits are broken.
In support of this I offer the "shoe is on the other foot" evaluation of:
1). A street samurai with an undetectable, unstoppable, magical widget that let him summon 4-8 mercenaries who can fly, have mil-spec armor and can melt through walls would be just as problematic.
2). A Rigger, whose entire premise is built upon using allied drones to fight for him, cannot take them anywhere he likes, undetected and unstoppably make them appear wherever he likes. Moreover those drones are not as strong as a mage's spirits, cost far more and are far more fragile. Even worse take the drones away from a rigger and he's loses about 80%-90% of his effectiveness/ utility. Take the spirits away from a mage and he still has equal or more effectiveness than a rigger.
3). Do i need a 3? Ok imagine if an adept could instantly add 4-8 additional attacks per pass with a moments preparation.
In summation: having 4-8 force 6 spirits available to a REGULAR mage (no crazy builds required) adds nothing to the game and only risks rendering the rest of the team irrelevant OR forcing the game to devolve into mini-game of spirit armies fighting one another (as the corpse mage summons his own spirit army to counter). Therefore Binding is broken as written. Instead of a fixed number of spirits, tied to a common drain stat (cha), Binding limits should start small and ramp as power progresses.
A couple good ways to ramp this power could be:
1). tie the number of bound spirits to initiate grade, possibly requiring additional metamagics to use more than 1 or 2 simultaneously.
2). tie the total force of spirits in use at any one time to initiate grade, so it starts off within reason and ramps as the mage gains power.