Well... i don´t belive that all bases must be larger ones. Normally, i build my main base as a research complex and ground forces base. A second one, very few kilometers away, is the workshop base. I build 5 workshops, 3 living quarters and the rest of the installations except defenses and radar (no radar needed anyway, because the base is "sticked" to the main one. An UFO storage is near too.
Two more bases as Air Bases; one in Venezuela (i can cover North and South America whit Saracens) and China (covering Australia, Pacific, north Russia, India...). The rest are radar bases, with only radar, command center, energy plant.
The game is very flexible, so, is matter of think about the best solution for a game or how do you want to play. For example, you can build a main base only with soldiers, another one with research/workshops, or maybe a little one with the basics plus storage, living quarters and labs...
