That makes more sense, but it's still drastically more expensive than simple command passing, and it scales terribly once you start considering anything beyond 1v1 because you have far more data to send and exponentially more calculations to make.
computation wise, yes it is much more expensive. i don't know (and i don't think anyone can get a good grip without running tests) how much more expensive though. i think a lot of it could be done fairly cheaply (are there any units withing X radius of Y unit; if yes then send data to other player(s)) and with effort could be optimized. the general continued increase in the power of computers is also something to consider but it should not be bet on.
as for game size scaling, i can't think of anything other then the general increase in the number of players as LoS is shared but it certainly ramps up fast. a 2v2 generally has twice as many units and, at a rough guess, twice as many calculations. a 4v4...
anyway i'm to tired to take this any further right now and my programming experience is limited so i'll leave it here for now at least.