I have been going through a phase playing wide and looking at the downsides and upsides so I have some things to say:
1. All this is great and would reduce the penalties a bit by quickly getting cities up to speed, however, it still doesn't erase the fact that settling late is never worth it from a cultural standpoint. Each city in the late policy game adds 10-20% on costs that are already like 2000+ depending on map size standard->huge. This is massive and no new city will ever overcome it. I think the real issue is the policy nerf so either quickly finish out all the ones you care about or reduce the penalty in your mod. I've just gotten into the habit of zooming through the trees early and not caring when I nerf them by expanding. Religious buildings that you can buy help with this and border expansion immensely due to the instant happiness and culture.
2. I've found the science penalties hardly matter. So you lose a turn off the next 3 or so? I don't care...I'm probably already ahead. Plus, unless you're founding in the modern era the city will eventually be science positive, Just ship a food ship over there and purchase aqueduct. with the order policy that city will be huge in no time.
I shoot for finishing all my settlements by early industrial as I looked at average tech costs vs. science output in cities and average progression rates and this seemed the break-away point. All cities built before this point will do okay...any built after never seem to get up to speed due to the massive amounts of new buildings and the fact that your core cities are so much bigger.
For vanilla here were my average science cost results and calculations:
(age, cost, 5% increase)
- Ancient: 55, 2.75
- Classical: 105, 5.25
- Medieval, prior education: 335, 16.75
- Medieval, after education: 460, 23
- early renaissance: 790, 39.5
- later renaissance: 1360, 68
- industrial: 2800, 140
- modern: 4700, 235
- atomic: 5400, 270
- information: 6000, 300
Notice the giant jump in cost penalty when industrial starts due to the higher base cost of sciences. Because of this completing all settlements by late renaissance is advised. Doing late renaissance strategy: you need to overcome 68 science per with each new city. This is easy. If they are probably taking you 7 turns: 68/7 = 10. So get 5 pop plus library and university. done. The city is no longer losing you science points and from thereafter if you keep it fast-growing will probably help your science. Policy costs, however, at this point end up nearly impossible to overcome with new cities.
3. Moving the order policy resettlement is a brilliant idea. It comes so late I'm usually done colonizing so if it helps it only helps with a few cities. This is because as I said, in the modern era it's too late to build a new city and make up the loss in science in all likelihood.
4. The order policy -33% purchase costs in all cities, and especially with big Ben is killer. I just settled 6 new industrial cities with this strategy and its beginning to pay off in science after a lull due to the huge new populations, though my policy costs went through the roof. Having the -33% on purchases was amazing for colonization So maybe adding a purchase cost reducer to the exploration tree instead of giving free buildings? If you really care about the city you shouldn't be too cheap to buy some buildings--just hold off on bribing a few CS's for a dozen turns or so. I took aesthetics and piety as my empire was religious-wide strategy so my new cities had no trouble building monument-shrine-temple by themselves. I could then buy aqueducts, granaries for 650 gold. Buying a quick worker and one other cheap building put me around 1k for each city which is accetable for late-game income. Emphasize food, and worry about science buildings once pop hit 6 as they do almost nothing before then...not even worth buying...workers make a bigger difference than anything else.
5. Someone said an order policy of free workshop in every city. Or windmill? This is more balanced and helpful...the workshop takes forever to build in a new city--and production in new cities is sooo slow...plus once you have it it starts fending for itself in production. usually worth buying but it is an expensive one.
In summary: good idea, yes to moving resettlement, having all starter buildings is OP but a policy providing one of them might work, maybe try a gold-purchasing reduction to help you buy new buildings? Buffing harbors would work too.