In the endgame, after upgrading everything in Sacrament there is no reason to interact with Danos anymore. I think it would make sense, for him having building projects outside of Sacrament. I came up with 2 new building projects, but there are probably more, that could be a nice addition.
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Danos could repair all the broken bridges, of which there are plentiful of, all around the island. This could make traversal easier.
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I saw many people complain about the dark areas, so paying Danos to put up torches or some other lightsource, could help solve this issue, at least in the lategame.