It's not clear, given the reference to Quadruple Besiege, whether you mean this to be played on the (twisted‐toroidal) QB board, or merely on a normal rectangular 8×16 one. Even saying ‘on two boards’ doesn't really clarify things in that respect. Obviously this has effects on e.g. the meaning of ‘forward’.
Have you tested this? The usual restrictions on double‐move games (stop on giving check, one move per piece per turn, ⁊c) are there to retain some of the clarity of the original game; w/o restrictions things like rifle capture and pieces which can reach anywhere on an empty board (or indeed one with relatively few pieces) in one move become possible, though since you mention the former that may be your intent? Probably it'll be a bit too tactical for most tastes
It's not clear, given the reference to Quadruple Besiege, whether you mean this to be played on the (twisted‐toroidal) QB board, or merely on a normal rectangular 8×16 one. Even saying ‘on two boards’ doesn't really clarify things in that respect. Obviously this has effects on e.g. the meaning of ‘forward’.
Have you tested this? The usual restrictions on double‐move games (stop on giving check, one move per piece per turn, ⁊c) are there to retain some of the clarity of the original game; w/o restrictions things like rifle capture and pieces which can reach anywhere on an empty board (or indeed one with relatively few pieces) in one move become possible, though since you mention the former that may be your intent? Probably it'll be a bit too tactical for most tastes