[quote:355es1tp]So, what I am striving to do is creating a sandbox-RTS and virtually "eliminating" limits for unit count and map sizes.[/quote:355es1tp]
Still your going to be limited somewhere in that.
I was thinking to deal with this you might treat the map like solar systems. I mean in essence they are round. So if you think in terms of staying within one system at a time, and if you were to go one direction you would eventually wrap around to the same coords you started from. You could then have different layouts for different solar systems.
Now as to unit counts, you could, in theory, use one sprite for all, and then have a separate frame for a different unit type. Of course for logic's sake you probably wouldn't want just one sprite, but you could cut down on extra sprites using separate frames.