Interestingly enough this implies that the primary qualification to getting an electoral vote is having an army and being willing to weigh in on an internal empire power struggle.
So Laurelorn has the basics.
I'm curious how 'in the empire' applies to other kingdoms, given we've got the time of three emperors precedent, where they were each claiming exclusive sovereignity over their territory but also maintaining their claim to an electoral seat that has influence over the other two. It seems like there's room for flex here.
If I had to put down the main disqualification, it would be internal/External identification.
It's a 'soft' issue that is a very heavy 'hard' block to them joining the empire that isn't 'being conquered'.
Even ignoring the fact that the elf's very much don't think of themselves as 'imperial' or want to.
The imperials need to also need to start thinking 'these are our elf's' before those types of questions are a serious topic without get push back from all quarters.
E.g does the group set off the empires 'close ranks against outsiders' instinct
The Moot gambit worked because it was very much an internal group making a power grab. Halfings are very much historically, culturally and politically'part of the empire' so it was very much internal politics.
The elf's are very much external acters trying to get in this theoretical situation.
While it's a bit.. off to think about, the elf's would have to become far far more integrated with the grater empire society, politically and culturally (or somewhat the other way around) before this is a serious discussion.
Basically, if/when the average middle class Enoir starts dressing in puffy clothes and giant hats with fathers, has a favourite middenball team, got invoked in a Aldorf riot over some cause they don't remember when on a student exchange in their youth, and regularly sends letter to business partners/old friends around the empire…
That's when 'do they join the empire' will be a serious conversation.
But that kind of cultural change, especially with elf's, will not be within Mathy's life time.
If they would be joining before that, guns will be invoked. And I don't want that.