Can HPL2 do this? (Texture swapping based on camera)

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Do you mean there would have to be differently-sized script areas for every possible monitor resolution (daunting, and maybe impossible if Amnesia supports custom resolutions)?
Or do you mean there would have to be different ones based on possible monitor ratios, i.e. 5:4, 16:9, 16:10 (which seems a lot more doable)?

I wouldn't say it is as daunting as it sounds. You should be able to find a sweet spot for most resolutions. Just take into consideration one resolution, like 1024x[height], and work around that, forgetting about smaller sizes. Full conversions can suggest what resolution the game should start at, but the player can change that resolution at any given time. There's no way to detect what resolution the player is using through scripts, but if you keep to one standard, that shouldn't be an issue. If some players miss out because they choose to play on dated hardware, i would argue that's their problem.