Tenryu, thanks, and sorry for the quandry.
Thanks too, Oleg - I understand now what's going on with the space ports - naturally you're right (although I don't think it's really the first thing it will build on all planets, but that's not the main point). What I would need, then, is an ability that is considered system-wide... hmm... I can't think of one off hand that wouldn't have side effects.
Or, like you suggest, maybe I should just add a new facility, like "Military Space Port" or "Industrial Space Port" or ... that is more expensive but combines space port with some other function that is useful to have on multiple planets in a system. Then it'd still be a quirk of the AI to invest in one of those on each planet, but at least it'd be useful rather than redundant.
PvK