Hi Simon,
That is a great list indeed!
I was pondering your list for a while,and came to the conclusion that one particular brand was missing, and a country known for a large variety of slightly more exuberant pens than mentioned in your list isn't represented either.
I think the missing brand is Waterman and the pen probably an Expert, a Hemisphère, or maybe even a Liaison.
The missing country to me is Italy. I think an Aurora 88 would not be wrong in that collection, in black with gold trim of course, or a Talentum. An Omas would be ok too, but those are more expensive. Of course best would be a Stipula, IMO, maybe a Florentia in black

. And there is plenty of opportunity to go wild here, colour-, material, nib-, and pricewise if you wanted too

.
Of course a collection is never complete, and although for now it may look like it is complete, there will be a time, once you're close to your goals, that new pens come automagically onto your horizon, to extend your collection requirements

.
I hope I didn't discourage you now

. Probably not

.
Warm regards, Wim