I don't see why it wouldn't be possible for an end user with soldering skills to take apart an Xbox wireless headset earpiece, remove the speaker and mic elements and wire in 3.5mm jacks where they connect. Put it in a small project box w/ a belt clip and connect it to PC360s or your headset of choice. Boom, no connection to the controller anymore. Or incorporate this Xbox wireless headset chip into higher quality wireless cans+mic to eliminate more wires. Or even add a Kleer high resolution audio transmitter chip from their evaluation kit
or an off the shelf transmitter and a matching receiver connected to your audio system and it's even more "wireless" (and higher quality than other 2.4/5.8 bandwidth traditional wireless.) No, these likely could not be sold as an off the shelf product (would not meet M$ approval), but for a home hobbyist it might be possible to accomplish.
PS- if someone does want to try to take this on as a project, I don't mind putting the idea out there for free, but please send me one for the courtesy (and don't try to sell them for a profit or the goons from M$ may come after you!)