Can you not provide some method to access the firmware and manager software? People can troubleshoot and what not on their own. You don't have to officially support it.
I bought a XIM Edge towards the end of the last gen life cycle. Had to step away from gaming for a bit and come back to find it's completely obsolete. Your point about old devices not supporting new OS's is well-taken, but people aren't asking for the latest and greatest versions of XIM firmware, just access to the most recent Edge firmware.
$120 isn't a drop in the bucket. That's on par with a nice gaming headset. Using that as an example, when the X1/PS4 were released TB/Astro/etc. provided a method for their customers to use that hardware with the next-gen consoles. You did that too, which is awesome. It'd just be nice if we could still access that software.