surely the camera and tracking positions of these devices can pinpoint offside... however, it'd be a FIFA rule if they used ths kind of technology. OPTA can distinguish shirt colours, heat maps etc... so it can't be far off
A tiny tag (smaller than a micro SIM card) could easily be built into the matchday shirts, usually the collar, to eliminate offside issues. It’s already working technology built into warehouse staff uniforms (I won’t name and shame the company) for monitoring performance and can tell you to the millimetre where someone is on the floor at any given time. Each tag costs less than 50p and is programmable with a machine costing less than £1500 in about 30 seconds.
I also very much expect the technology in the ball can be adapted although admittedly I know far less about this to record a change in direction or velocity, at any given time.
A simple algorithm could then tell you if a player is offside, determined by the tags and ball data at any time. Decisions on interference would still be VAR, however the tags would completely rule out marginal offside decisions. Even if the exact timing has to come from a human, it would still be a selection of ball movements to choose from and not a guess.