According to recorded videos from //build/ 2013 conference, Win8.1 will support (again) I/O devices. Fortunately MS offers a Win8.1 Pro preview installation ISO (lasts until January 2014), which does work on VirtualBox VM, so I could quickly test it out.
Even though I didn't spend more than 5 minutes fiddling with it, (virtualised) Win8.1 could pair with the CAT-to-BT adapter (HC-05 derivative), correctly assign two COM ports and Ham Radio Deluxe connect to the radio.
The whole process still seems a bit buggy as OS level, but at least this kind of I/O will be possible with newer computers too.