not a higher unit cap, but if its in a more strategically sound area (less distance from the front line, dont have to travel through AI planets, or something) then it might be useful.
For instance in my games, the first one tends to have higher priority than the others, but I also seem to go for ARS before a mk4 factory.
Although core:bomber factories are something i love; core bombers are awesome, but I dont seem to have mk3 bombers often to make mk4 ones :p
