There will definitely be *some* channel closures, so other things equal routing fees will be higher than usual for a while.
Here's a very detailed breakdown of the logic and game theory of various ways things could go (without guaging the likelihood of the various outcomes) by Start9 https://start9.com/bip110/
Sure, yep, the physical world may be small, but certainly numbers go on for a while and certainly we can can find an unused NIP*** or of need be NIP****
I'm an ignorant pleb, but why change an existant NIP so drastically instead of introducing a new one for this spec? Seems to me that retroactive changes are dangerous, even if the old spec was shitty.
It was a lot of typing, and a lot of good thinking.. I only joke because the typo was near the end of your brink wall of text, and I didn't enjoy how I saw myself in your other options.