In my recent game, I replaced the constructors with a faster ship that has constructor modules, and I obsoleted the original constructor.

I then discovered that I cannot actually build new mining starbases anymore - the new ships (Builders) will not automatically build a starbase when they hit the resource, and if I choose "construct", then I'll only get the regular menu of influence/military/economy starbases. I think I'm totally blocked out of building mining starbases, unless I'm missing something.