I understand that multi-layer bondage is a fetish in and of itself, but in the game it goes way too far, to the detriment of common sense, visuals, and ejoyment. In other words, the sheer amount of restraints that can be stacked on top of each other are completely detatched from reality, all the different colors will make the player look like a rainbow clown, and these two together are completely immersion-breaking. Multiple straitjackets, armbinders, boxbinders stacking on top of each other AND with cuffs and ropes and slime and whatnot is just silly.
The solution would be rather simple, and Daent's The bondage of Eliza has a similar system already, restraints have layers and slots, no two restraints can occupy the same layer and slot at the same time. I'd add to this the shape of the restraint, which has to match between restraints that occupy the same slot but different layers.
I propose there to be the following layers:
-Underlayer: things that are either completely skin-tight or go inside the body. Latex stockings, catsuits, mouth stuffings, earplugs, plugs, tape mittens etc.
-Heavy garment layer: corsets and boots of various sorts, also ball gags. These are things that are almost completely skin-tight or partially go inside the body.
-Normal restraint layer: cuffs, ropes, OTM and OTN gags , muzzle gags, leather mittens, straitjackets.
-Cover restraints: stuff that has room inside to plausibly fit other restraints while still being tight itself. Box binders, armbinders, legbinders, sensory deprivation hoods.
-Cover restraint harnesses: armbinder harnesses
-Encasement: slime, rubber spray, etc. These should never be things that are applied by actual human beings, but the inevitable consequence of environmental hazard and creatures that try to cover you completely.
Some examples of what would and what would not be possible:
Being box-tied with rope, having tape mittens, leather mittens, and wearing a box-binder: possible. The two mittens occupy the same slots (hands) but different layers, and the same goes for the box-tie rope and the binder. The box-tie and the binder have matching shapes, and the mittens themselves don't have a shape in and of themselves to conflict.
Wearing a latex legbinder and a high-sexurity legbinder: not possible, they occupy the same slot.
Wearing 3 different body harnesses (a big issue right now, as harnesses are very abundant): not possible, they occupy the same slot.
Multi layer-gag: stuffing, ball gag, muzzle: possible.
In particular cases, it might be desireble to allow restraints to occupy more than one layers. For example, maybe we want to make OTN cloth gags mutually exclusive with leather hoods.
If enemies want to re-bind the player with more secure restraints, they might have to remove existing ones first. This would open up new avenues of gameplay, for example, the player could use the opportunity to try to break free, or the enemy might have to work strategically, maybe use some sort of bondage furniture to keep the player in place, only freeing as little of the player as possible at once, re-binding them in steps.