Type IV subclassing is largely orthogonal to other types; should it partake in the exit criteria?

[mgaudet]

When reading the explainer for this proposal, one thing that I found unclear is that it feels as if (and the exit criteria in particular help enhance this feeling) that the subclassing types are a tower of progression: Type IV implies you must have Type III implies Type II implies Type I sort of.

I've been experimenting with what it would look like implementation wise to actually disable these various subclassings, and I really get the impression that Type IV is special; not really part of the 'tower'.

Which is to say, it feels like it's possible that we could decide Type III is worth removing, even if Type IV isn't web compatible.

The question then being: Should Type IV partake in the exit criteria?

[mgaudet]

(To be clear: I would argue that all the RegExp Type IV subclassing should be removed regardless of larger questions in this proposal)