I agreed, for CF it depends at which age you're staying when aiming for lvl200. Staying for example at CA or anywhere as high as SAA:B could still be arguable interesting. In preparation for hydra200 when rushing towards SA:T to grind for the goods. Assuming it's worth it to hit space hub. Collecting the diamonds along the way for the expansions.I would say this is situation dependent on how long it took to Age up (on a diamond perspective)
Level 200 Chateau Frontenac is amazing, but we've already received Space Hub announcement that makes it sound like we'll only get one more age added, and then no more Ages. So it'll be incredibly valuable in Iron Age if you then Age up and start going through the Maps triggering all the diamond quests. But if you're already in Titan it's probably a moot point on whether you get it to 200 or some other level
If it's for goods then it'll depend on how much you really need those goods. Someone regularly selling goods would make good use of it. Someone donating to treasury would have use of it. Someone only using goods when quests require it won't need a level 200 chateau just for goods.
For this I'd put Observatory on top for Lvl 200 Treasury Goods producer. They all increase 2 goods per level no matter what, so lvl 200 Observatory would at least be increasing Blue Stats + be the cheapest treasury building
I wonder how much longer a person with lvl 200 Seed Vault would be playing to make use of that?
Probably the most futureproof building to level on a military basis.
Overall the easiest and most straight forward is AO201, assuming same age combat is utilised regularly. For hydra200 I think at least for the moment St. Marcus is needed for the coins. Although an high castle level and a number of special buildings providing coins boosts could assist greatly too. As for the goods, an CF200+ could be invaluable to fund such ambitious project. Though I feel it's more an odyssey for the bragging rights and maxing out % efficiency. I find it hard to believe something else with an efficiency of 37,5%/ and 450/ will come along to outperform it. For reference STD's top1% spawner has an efficiency of 5%/ but no road connection needed. Although the fp requirement will be astronomical. I think it might be theoretically achievable through high fp efficiency, consistent X% and active shipping with Arc180. Although I admittedly didn't do the math and I'm unsure if anyone knows the total costs for hydra200.
Personally I'd like to at least give it a try. Pushing first AO201 and than trying to pushing for hydra200. Although it depends on how the space hub will turn out. It it'll be more comparable to SA:JM I think it might be worth it. If it's more like SA:T it's probably not worth the trouble for 450%.