indeed size limits would be a problem. some time ago i thought of the spanish empire vs portuguese empire. but as you can see from the image below it's pretty big:
“In the beginning God said, the four-dimensional divergence of an antisymmetric, second rank tensor equals zero, and there was light, and it was good. And on the seventh day he rested.”- Michio Kaku
I'm going to try to restart the High Seas map that died a few months ago, with the water as the playable area and the land dead space, which has nothing to do with the post other than I wanted to say that in working on it I have decided that just because you are representing the world doesn't mean it has to be entirely accurate. You don't have to truly represent the size of the oceans - make the land 2/3 of the globe and fudge the oceans, which are just dead space anyway. And get creative with the type of projection you use.
this is what I'm toying with for the high seas - the land is going to get even smaller since the water is what i need to focus on.