Please, everyone, remember that one of the major reasons Harvesters got a buff way back when (March?) was to relieve the downtime problem. If harvesters get nerfed again, the downtime problem in increased again.
I, for one, have greatly enjoyed being able to rebuild my fleet in a more reasonable amount of time, even if it has cut into my reading time.
FYI, what I'm leaning toward right now is making command station upgrades drop some kind of foldout-like structure on your home command station world(s) that gives some/all of the bonus. Though some care is necessary as people might do some crazy things with both logistics and military effects on their HW... but generally I find HW-defense more entertaining to read about anyway
To go back to something to something older: What about... modular Command Stations? Unlocks give new modules (Resource Manufactorum Mk II, Time Dilation Field Mk III, etc) that could be assembled on an empty command station shell to produce whatever is desired.
Unlocking Mk II/III Harvesters could unlock the Command Station resource producing modules, while forcefields, turrets, etc could unlock the modules (whatever they may be).
I'm not sure what providing logistic or military station like buffs to the HW will do in the medium-to-long game, since I usually secure/neuter my local systems early in the game.