I doubt that client-side processing is ever going to be implemented to the extent that some people would like to see. Not only is it a complicated task, but it would be hard to find a good, general purpose solution.

One form of client-side processing that would come in handy is client-side visual effects. I am guessing that the missile proc sends a single command to the client and the client handles the visual effect entirely (if this isn't the case, why not?). If this is the case, there's no efficient way to reproduce the missile proc. You can set an object's loc and pixel offsets every tick to mimic missile's behavior, but this would be sending updates to every client every tick. If you wanted to make simple changes to missile (change the projectile's speed, give it an arced path, etc.) you'd have to implement the effect yourself. With enough projectiles, this could cause a severe performance hit.

The main purpose is to create visual effects so the client code shouldn't need to modify anything but the objects used to create the effect. Likewise, the server doesn't need to be notified of anything done by the client proc since these objects only exist on that client. Everything the client needs to know will be passed as a parameter, so there's no situation where the client would need some data and not have it.

The client code is handled so differently that it could be its own type of code file (since the client procs aren't mixed in with server code, there's no confusion about what you can or can't do). Depending on how it would be handled on the client end, it may not even have to be DM code at all.

Any thoughts?