so, i downloaded K-Mod and gave my feudalism rush idea a try.
so the idea here is to oracle feudalism, which gives you a.) HR, b.) longbows, c.) serfdom for fast workers and super river farms, and d.) vassalage, which supports extra military units (which I guess is nice for K-Mod which requires a larger standing army) and lower city maintenance costs for a bigger REX. essentially, the goal to get a huge empire covered in 3F3C and 2F1H3C farms. so, started a game as Mansa Musa of the Mali (so that I could switch back to slavery if I needed to), pangaea low sea level (to give this strategy a bit more of a chance to do well), and Emperor difficulty. (due to everybody scaring me about the K-Mod AIs
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my start was kinda weak; only food was a dry rice and a grassland cow; had a grassland gems but only 3 total river tiles in the BFC. oracled feudalism @ 1400 BC, and then proceeded to REX. status at 1 AD is that I have 10 cities, with room for at least 5 or 6 more. I have a tech lead (about tied with Zara, but the two of us are 3-4 techs above everyone else) but am only gaining about ~125 BPT, yuck. only 2 cities have libraries, and only have 7 or 8 workers total - wish I had at least 4 more. no academy, as I slow-built the ToA and that popped a great merchant instead of a scientist.
(was originally building for failgold, but started panicking when Zara's culture started clobbering me). not sure how necessary an academy is anyways, as vassalage is actually pretty good for this strategy.
so, overall the strategy feels kinda weak. part of the problem is the food-weak capital led to slow rexing, and also most of the land I'm expanding into is covered in jungle leads to slow rampup in the new cities. serfdom has actually been pretty helpful for that. i've also built quite a bit more military than I ordinarily would, I guess because I was scared of the K-Mod AIs. LOTS of early declarations of war, although luckily none on me. I only switched back into slavery twice, during which I tried to whip each city twice. I think, if I were someone like vicky, I might be able to avoid slavery completely. building the ToA was a mistake, even with Marble, because even though its nice to have, I'd trade it back for 2 workers and a settler certainly if I could.
at any rate, ~125 BPT, even with the prospect of that turning into ~300 or ~400 BPT in another few dozen turns I think is pretty weak. however, that's not to say that this new serfdom is all bad or even that my execution was most efficient. my core cities were nice and fat overall and I did certainly develop a lot of tiles, especially considering how many were jungle.
most likely, this serfdom I think has applications for financial civs early and late; early for transition towards a specialist economy, producing serious beakers in the BC years while maintaining a low GPP profile, for a later transition to caste (so this would be particularly good for Liz) and then later still to whip-heaven. willem (fin/cre) might also do well because of cheap libraries. I think, if I try this again, I'll pick one of the english queens, and regenerate the map until I find a capital with at least 2 good food and lots of river, and also to make sure I set up a heavily-hilled city early to make sure I can slow build lots of military without needing to switch into slavery too often. a continents map might also do better, as low AI contact means that the overall tech rate will slow, giving a chance to develop more tiles. will report how it goes!