Thunderbrd
C2C War Dog
Nothing of AIAndy's stuff in use, it still uses all the default tags.
The current (default) validity tags are not simple in that without understanding their precedence order the new tags you are proposed may not work as advertised.
For example in ImprovementInfos, HillsMakesValid, and FreshwaterMakesValid (and a few other tags) override all other conditions. So even if you only included a narrow set of terrains or features marked as valid, the improvement would still be buildable on terrains you did not specify if it was sitting on a hill or on a tile marked as having access to fresh water. (Like how farms can be build on Tundras if and only if they have freshwater, even though Tundras are not listed in its set of valid terrains.) Thus depending on where you put your Peak, NotOnPeak checks, it might just ignore your NotOnPeak flag if it already passed FreshwaterMakesValid, and so on. I dont know what the actual code looks like that evaluates all those things, so I dont know what order it does stuff in. All I am saying is it may not be a straighforward as you are hoping.
IF you want a finer level of control of what improvements are allowed where, we may need to use the more robust bonusInfo valid placement checking, which allows a per terrain, per feature and per terrain+feature combo checks.
Ah... there's certainly some things to consider there. I can work around that but it's good to know. So those conditions are some you would NOT want to override the peak checks right?