I'd love this and I'll try to do it if someone hasn't done it by the time I'm doing updating my profile pic mod.
I prefer continuous build because it lets you set a looping mix of units (like 1 flame tank, 5 ants).
In the factory blueprint, add the following: Code: "factory": { "default_build_stance": "Continuous" } I presume it's a client-side value, but haven't actually tested. You can probably set a default unit to build too: Code: "factory": { "initial_build_spec": "<path to unit blueprint>", } (Again, untested)
It's the unit blueprints, eg: \pa\units\land\bot_factory\bot_factory.json The factory attribute should already be there, just have to add default_build_stance/initial_build_spec.
I had considered that as the next step, but it would be quite a massive update code-wise, and limited as the settings would only be changeable from the settings menu (and global). It might come in the far future, but time is in short supply.