Z-Wave by definition doesn't require a cloud.
What I'd do is just add more z-wave devices to your mesh- any AC-powered Z-Wave device will act as a repeater. That could be a plug in wall module, light switch, other gadget, etc.
That sort of thing. Put 2 or 3 in a line from the hub to the GE relay box (and of course include them to your z-wave mesh) and that should work.