As for the 50/50, that was just an example; there could be three settings: Majority Fighters; majority Bombers; and 50/50.
.. which could then be expanded into preset rations, 10:1, 9:1, 8:1, 7:1....1:1

And on and on. This is why there is no default production, because everyone wants something that they'll use, and that differs for everyone. And besides, having "settings" defeats the whole purpose of your initial post, which was to have hands-off building - since you'd still have to select how you want them to auto-build

says he the only reason he is not getting it is because he hates the constant micro of bomber-fighter-bomber-fighter . . .
Well, if he wants to make life hard for himself.. or he could just wait until they're all built and do it once. It's not like filtering reinforcements in one ship at a time is ever a good idea

I know I come off harsh, but you're basically asking for a mechanics change because you're making your own gameplay harder than it should be