I know you are probably overloaded with requests and suggestions but I figured I'd add a couple in case you get bored :)
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custom breast rendering this would be about having the breasts move and change shape as well as possibly configuring the size. I guess it would be pretty complex something like the eye code with custom shading and shape parameters. The idea would be that a push up bra would create some lift and combined with a sports top that would create even more. If you damage the top(s) then the breasts would drop down a bit and bounce.

guess the clothes would need to have access to part of the shading which does make it difficult to do.

breasts have internal ligaments like a sort of elastic so it will start to stretch and snap eventually. if the breasts get damaged they would tend to change shape possibly start to sag and not bounce back to the original position anymore.

Anyway you probably get the general idea it's probably too much work though.
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The other idea was transmitter receiver sets. I had some idea about custom character reactions so they respond to each other but this might be a bit easier to implement. You could have a transmitter that picks up pleasure or pain and attaches to the head or gets inserted into the pussy. A receiver could attach to a body part on the same or a different girl and get activated by some settings.

So if the girl with the transmitter got aroused or felt some pain the receiver might start to work and do some damage e.g. start to cut a limb or if it was inserted in the pussy or attached to a breast it could do something there too. It could also only work for orgasms or have some sensitivity setting. I guess also something like random or sequential activation if you had a set or receivers. Probably tons of variations on that idea.