Those are excellent ideas, and definitely the same lines I'm thinking along.
I do wonder about your use of "concordance", which essentially means harmony or concord...
Yeah, I almost elaborated, but didn't. I used concordance to bring to mind artifacts...but a better term would be discordance, which may suit your sub-goal of introducing new crunchy things. So rather than concordance (harmony) with the mountain, the PCs become more discordant with it, as if the PCs are a virus the host is trying to exterminate. If we think of the mountain as an artifact (or perhaps the Arcane Engine thingamajig that ports it around), then a concordance-like structure lends some parallels.
One thing comes to mind. Whatever you choose, the increasing difficulty might be too much if there is too much of a spread between encounter levels. That is, if the spread in encounters is about 5 levels, High discordance would be a severe penalty and effectively the spread may be more like 10 levels (level 1 encounter no discordance to level 5 encounter with 5 discordance eg). You might need to adjust xp when under discordance, flatten the spread a bit (2 or 3 levels eg), or both.
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