Hey, I haven't been brave enough to try it, but have you ReWired in Live to Reaper and been able to use your script without deselecting Live as a control surface in it's own MIDI preferences? Live 10 now supports Live taking control of Push 1 & 2 while in ReWire slave mode.
The obvious thing is to deselect it in MIDI preferences in Live, just wondering if there was any way to switch between them without major hiccups?
I'm a power hungry slob I know!