how about this the more nexuses you build and the farther away you build them the less resources they gather, so for instance if you have like a third nexus in the middle of the map somewhere the probe brings in 3 minerals and then you have to fix this by building some kind of a relay station like power lines or something that has to power the nexus up.
I got this idea from this awesome game called Alpha Wars, its an mmoRTS (thats fuckin right) the more bases you capture there the slower are resources, this will nullify those tryhard faggots who are always like "ooh expand brah youre not a pro homey" and how about this you can build some sort of a CITY in your main base like have skyscrapers or something cuz its yoru main base and its industrialized an all that.
Alpha Wars.
http://uk.alpha-wars.com/?r= created in Germany.