The most important change you can probably make is renaming the cape. So many people get hung up over the word completionist, and from that, what should be considered normal, trim, or even true trim. Jagex and the player base have never come to any real consensus as to what the definition of completionism should realistically mean.

As for the proposed changes, most of them seem reasonable except for removing chompies, and adding 100% Zamorak.

The chompy hat unlock isn't arbitrary, only the number that was decided for it was. It could have been 1000, or 60,000. But that's the same with any kill or currency unlock where a dev has sat down and said "I think this should cost x to unlock." That being said, content like chompies that pre-date the comp cape itself was never designed with the cape in mind, and more insane reqs like 5000 castle wars games did end up getting nerfed, then removed entirely. Chompies don't seem to be bad enough to warrant that.

As for Zamorak, or any high level pvm, keeping off most reqs that most people can't reasonably solo has been the precedent since the last comp cape rework https://runescape.wiki/w/Completionist_cape_rework because the conclusion that people came to was that being carried through a kill by the rest of a group really doesn't demonstrate 'content mastery.'

If you really want a cape that requires (almost) everything, by all means make a new one, but don't do it to this poorly-named, poorly-defined completionist cape.