I've seen some IM platforms (namely Revolt and
Guilded) have the ability to
let the user reference multiple messages in a single reply, which might be
a useful feature. I think with the XEP as it currently is, it could be
fairly simple to add support for this feature.
I'm interested to see a prototype of this rnd especially what kinds of UX
are possible for multiple replies but no quotes.
Until then I think any discussion of XEP changes or namespace bumps is a bit
cart before the horse.