I still can't get my head around E4 for WSS can make any sense in this context....
You've already explained it:
Or you could get a route with a few bouldery sections, but well protected. Harder to onsight, due to technical sequences. E4 6b.
Now imagine the same route with a single bouldery section and make the rest easier climbing - to still get E4 the move would have to be harder, so E4 6c yes?
Now make the route very short, barely a route at all, and put that single hardest move right on the floor...
Yes, I think a big part of the problem is the focus on 'onsightable'. I've never done a route where the E-grade is higher because it's hard to read. Astra on Pavey is the perfect example - steady E2 IF you find the hidden hold on the crux. Totally blind. It gets E2, would be E3 if you pushed through without. Have you any counter-examples?
On the above WSS example, grades have followed the logic above rather than placing a lower limit on what an average E4 climber could onsight, because otherwise you just end up binning all the bouldery routes into less grades, which gives less information. As I keep saying, the grade isn't E4, it's E4 7a. 7a tells E4 climbers they haven't a cat in hell's chance of onsighting it, but they can have a go without consequence. Verandah buttress is HVD 5b likewise.
some of the confusion in the harder grades would be reduced if we just binned the UK tech. grade substituting French or Font. grades as applicable. There is no requirement an E grade has to be followed by UK6c or something equally ambiguous.
Some, maybe. It wouldn't solve anything for me - mostly because I don't see big problems. Grades are subjective. Going to a narrower scale like Font grades gives an illusion of greater precision without necessarily increasing accuracy. Plus in Font, the scary highballs have easier moves - presumably we ignore these (not to mention traverse grades!!).
I find grading interesting - it arises universally with systems that should be easily translatable, but aren't, because simple number scales become imbued with cultural differences. I think it's more interesting to try to understand the differences in application than to try to homogenise them. Nobody's stopping anyone using all the scales when they discuss a route.
