I have a suggestion about ground force construction...
I suppose we already got over this - make ground forces build-able with standard construction factories or make GFCFs function similarly to construction and/or fighter factories.
I think we essentially need 2 types of factories - construction factories, the ones that build structures and static installations;
and unit factories - they construct ground units/fighters/ship components and space-sta-... hm... I'm not sure about shipyards and space-stations though. But I guess you get the point.
Now about ground forces - I suggest using a system similar to the one in Pacific Storm game:
your unit factories produce land units, which are unassigned to any formation and put into a planet's stockpile. You open a ground force window, create an empty formation, and assign your created ground units to the newly created formation.
It may of course could clutter your troop transport order window with unassigned land units, but it shouldn't be a problem if you assign them to formations.
Other suggestions/reminders - it would be a good option for ground HQ units to have range selection when designing them, at which they could provide bonuses to units in different solar system, just different planet, or only the planet they are stationed on.