Very interesting discussion.

Haven't started to play yet as I just finished reading and then reviewed the save to see what I could add.
The biggest issue seems to be Gold for upgrade.

Thinking about it, we have to decide how important our Rep is in this game. If it is not important, then we declare on Babylon.

That still only allows us one upgrade every 2 turns, painfully slow but better than one every 4 turns. Should we declare, how much is it going to cost to gain some allies? We have Monotheism that some of them may want, after we build the embassies we will need?
I also understand that we do NOT want to obtain Feudalism until we have enough upgraded EuroSwords. No option looks particularly promising.
Looking at the save, we have about 19 or 20 Vet Warriors ready for upgrade. The problem with this, besides Gold, will be filling in for the Vets on MP duty so they can leave and attack China. I think we should change the builds in the outlaying cities to Warrior to make Reg Warriors to backfill the Vets.
There are 3 Settlers due next turn and I think we should build them because more towns mean more gold and more units supported. We should keep the settler factories going and build an Archer between 2 Settlers as much as we can, imho.
Looking at Agedincum for a FP, there are no bonus grasses there and, as Gator pointed out, it is on the 5 rings, so there is 33% corruption. It is producing 1 shield and will grow in 9 turns. We can build a Courthouse, but it is going to be a slow process. The only way I can see to speed things up is to merge a few workers, that we don't have to spare. The only other option is to build it on Ratae Coritanorum (wahtever it is??) which is producing 5 shields with one corrupt. So a FP would be available in 50 turns or less, with growth. It is also on ring 1, with 11% corruption. While less optimal, it may have to do.
I am going to wait to start because I think we have to decide about Babylon and the FP site. This is one of those critical junctures where I'd rather hear some more rather than march on and screw up!!
EDIT - Forgot to say that I do see your point Gator and believe we must change some inner ring cities to EuroSwords because even with declaration on Babylon, it will still take too long to do upgrades alone.