You forget that all your ground forces rely on vendarite to exist so in GC heavy games this could be a problem.
You are right... ground unit also uses Vendarite... I guess that the cost of building ground units really never impacted my economy that much so far.
Ground units can put some strain on the Vendarite situation depending on circumstances. A unit of 5000t of say medium vehicle tanks would cost you about 400 Vendarite while 5000t of regular infantry is 100 Vendarite, I don't think tech levels will make the cost higher or lower either so ground forces become less of a cost in terms of resources as your technology in mining gets more advanced, for ships this relationship is more linear except for hangar technology.
I hope that we in the the future get some sort of carrier love in terms of designing carriers and carrier operations. We now have very intricate systems for loading and firing of ordnance and handling of MSP and fuel yet parasite handling remain very abstracted and to be honest rather basic and not that realistic. But that is something for the future perhaps. If Steve ever create a campaign centred around heavy carrier warfare we might see some development in this area as that is how Steve tend to focus on mechanics.