VNC should be the ideal solution to this on a fast enough network ...and if vnc client can send a pen input to the host and host can see it as a proper HID device.
As far as I can tell this is not possible: https://tools.ietf.org/html/rfc6143#section-7.5.5
Also selecting a specific window, which is possible in Weylus, does not seem to work with vnc.