I can't see why you are not able to have an option to set the play wma demo buttons to an external player if you can't make an internal player for it.
I can't remember on Linux if it was looking for WMP to decompress the wma to wav or if you use an internal decompressor ?
You have the Win version, you have the Mac version, get this sorted and you will have a working Lin version.
The new way the BB VST works now it should work with the Linux version of Reaper.