In that discussion he actually suggest what I did in a reply on another thread, which is the basic buildings increase their output as they level up. It wasn't really new buildings as part of level up process.
But as for buildings and level ups in general I original didn't mention them cause I started the thread just to get something more added that was "simple" to get the ball rolling. I figure the unique level up options tied to what buildings a city has would be a bit more difficult to get through. I would honestly like to see a city level up setup more like the Feat choices in many RPGs. Curtain bonus would be unlocked by the resources they have access to, buildings in the city, current level, and so on.
So at level 1 you would have a couple bonuses to choose from. Then at level 2 you'd have even more including the level 1 bonus you didn't pick. The same at level 3 and so on. That way if you really like the level 1-2 bonuses you might take 5 of those when you level up your city to 5.
Here's some other ideas for level up tied to buildings/resources.
- Traveling Merchant - Requires Merchant and gives gildar bonus in addition to food to any trade routes coming from city.
- Miner's Union - Requires Miner's Guild and gives +% to Metal Production
- Farm's Union - Requires Farmer's Guild and gives +% to Food Production
- Organized Farming - Requires Farm, Irrigation, and Granary and gives +% food production
- Thriving Economy - Requires Merchant, Market Place, and Trade Center and gives +% to Gildar Production
- Experienced Armored Smiths - Requires Forge and gives +1 Def to units that have full armor (helm, chest, and leg pieces)
- Experienced Weapon Smiths - Requires Forge and gives +1 Atk to units that 1HD weapon and +2 Atk to 2HD weapons
- Arcane Affinity - Requires 2 Arcane labs and gives +1 mana regen to any units in city
- Book Worm - Requires 2 Lost Libraries and any Champion with the trait that gives +1 Tech in the city gives a +10% research bonus to city
- Gold Rush - Requires 2 Gold mines and gives +5 Prestige to city but -10% Gildar production from crime
- Welfare State - Requires 2 Refugee Camps and gives +10% to house but cost -5% Gildar to support the refugee influx.
These are just some of the ideas. Obvious the bonuses would need to go through balancing checking and what level they are would also depend on the buildings that they require such as Thriving Economy requires trade center so it would have to be a level 5 option since that's when you can build trade center and you'd have to pick after you got to level 5 and built the trade center which is another reason to put off the choice.
The multiple resource buildings needed though is a great way to encourage players to build fewer cities the encase more resources as they only way to get them would be to get multiple resources of the same type in one city. I only gave example of requiring 2 but it could also have 3 building requirement as I've had 3 gold mines in a single city before.
As for the + bonuses to units trained in the city I'm not sure the current system supports it. However since we have seen champoins with unique abilities it's likely to assume that you could possible give those unique abilites to normal troops. And then possible make one that simply gives the flat bonus much in the same way a lot of Civ 4 mods would do interesting things to units in the same way. The more the other areas of the game get fleshed out to have more variety and be more interesting the easier it becomes to think of city level up options.
This system also makes the upgrades feel more like they are tied to the unique features of your city rather then simply flat choice that everyone gets. Since not all cities will be the same a lot of times the level up choices between two of your cities will be very different and that is the way it should be since it makes them feel even more unique.