It's been 9 days since i started my Orbis and I'm about to finish it in the next few hours (not playing every day- family, etc). That's almost 3 weeks earlier than the deadline.
Yes, I'm building solo a large Tier 3 starport, and it's also a Primary Port, so the amount of hauling is even greater (~250.000 commodities).
The thing is, after you finish building one, you really, really don't want to build another one, at least in this lifetime. The FDev went really , really wrong with this, because instead of making the game more addictive, it's actually more annoying. This is how you lose players in the long-term.
My proposal: make it so at the beginning of every construction players will have to make a selection: solo or group building.
Keep the high amount of necessary commodities for players that are playing in a group.
For solo players don't allow anyone else to dock at the colonization ship/ construction site, but decrease a lot the required commodities.