This makes sense because VUhU are (usually binary) operators just like JOI and using them in other places than mekso makes sense.
# More flexibility
# Allowing mekso to be used in more places = more utility of a huge part of cmavo space
# Pretty much none. It makes things grammatical that weren't before, but it does not break any usage.
Definitions must be found for all the use cases, e.g.:
SUMTI VUhU SUMTI, SELBRI VUhU SELBRI etc
If VUhU *moves* to JOI, JOI has to get all the mekso definitions as well to make things like (1) grammatical:
(1) li pe'o joi paboi paboi du li re
So it might be easier to just give VUhU more rights and allowing it in places that JOI can go, but not vice versa.
(2) lo mu bakni su'i lo mu kanba cu zilkancu li pano lo danlu
"5 cows + 5 goats amount to 10 in animals"
(3) lo mi lanzu vu'u ba bo lo mensi noi cliva bilga cu zvati lo nunsla
"My family minus-later my sister, who had to leave, were at the party."
This removes some of the awkwardness of mekso and makes it more intuitive and less verbose. I opine that the above example sentences show a useful application of what this proposal entails.
This proposal is not very detailed yet, but I can flesh it out, should there be desire for constructive discussion.