fyi... I went out and edited all resource mining facilities (starbaseabilityvalue in starbasemodules.xml) down to 1 from (in most cases) 5. This gives you just 1% increase (after the initial 5%) for starbases on resources.  I just prefer not having the resources impact the game so much.  You have to be careful when editing starbasemodules.xml because there are quite a few mininig facilities for each race and the names are different.  First one seems to be mining barracks. So I guess the max return will be something like 10% vs 50% when you fully exploit a resource.  Maybe stardock can edit in a slider sometime in the future?  Hope this helps.