That... wasn't obvious.

I don't quite get people being opposed to stacking mexes. As mentioned, the T1 mex still generates income while you put a T2 mex over it, in addition to the T2 mex offering protection for the T1. Not that mexes are very durable anyway, but it's still better gaining simultaneous benefit from two structures coexisting than turning the T1 into the T2.

Solution would be just to automatically build t1 and then t2 on empty metal spot when you are buildinf t2 and there is no t1. There is never a situation where you wouldn't want to build more cost effective structure first. Not to mention that it takes like 2 .5 seconds for advanced fabber.

That would only be the most effective if you have excess metal to build with, in which case you shouldn't be expanding your mexes but expanding your energy and factory count.