Sure, but there's no evidence for it one way or another in the fluff. The only evidence we have of that is that it shows up with the merc tag on the MUL (unless I'm missing something somewhere, which is possible).
But again, that makes the Grim Reaper odd and unique still. Its not like they created a Master variant, or spotter variants. They made 2 Grim Reaper variants with slaves, and that's it.
Heck, they didn't even make an upgraded version that would integrate with mainline WoB forces that utilize c3i (not that there's anything wrong with running WoB forces without c3i).