I suppose it might be possible to do something like have flat areas on the map for artillery, for then to have some visual cue in the HUD when you're nice and steady. I'm not a coder, so I don't know.
To be frank, though, I don't really know if the artillery system is that necessary anyhow. I mean, sure, it's a good system, easy to use and everything, but surely it's not that important that we can't have artillery pieces if they can't utilize the system? I'd rather have a "stuka on foot" that fired rockets without the FH2 spotter system than to not have one at all. It really isn't harder than getting a forward observer to tell you where the shots are landing - you could even set up an Arty squad with the SL placing move markers where the shots impact, easily letting the person firing them know how he's aiming. And there's also the direct fire method - drive until you can see your target, then fire. Risky and not how it's supposed to be done, but still provides accurate fire.