Sorry, but for now I'm inclined to say no.
A chastity cage accessory would require a lot of artistic reworks to the many grapple images in the game, writing changes to every orgasm stage at least, mechanical testing and implementation to make sure it works with every enemy, balancing to make sure it doesn't become ridiculously OP with the Skimpy Covers...
It's not quite as simple as you make it out to be, but I mean no offense by that. It'd just be a LOT of work for a kink that both us devs are kinda "mid" about.