Given that Auto-Group system presently in FFXI will happily make a party of 6 Warriors, a competent party-making system would be a huge leap. Also, I'm not sure if there's even any six-person content in FFXI right now that I'd want to "experience" with five random people, so something like mini-Voidwatch might need to be added to make that system worthwhile.

That sounds like a lot of work and the posts about Seekers of Adoulin's effects on other updates make FFXI's Development Bros sound overworked already. Not saying this is a bad idea, but you definitely shouldn't expect it to actually happen.