I don't know if anybody has taken a good look at the rules.
For reference, here a breakdown of all possible origins of
Slavic final vowels:
o : *-a
*-o
a : *-a:, *-ã
*-o:
ja : *-ja:, *jã
*-jo:
o~ : *-a:N
jo~: *-ja:N
e : *-e(s)
je : *-je(s)
*-ja
*-jo
ê : *-ai(s), *-a:i(s), *-ãi(s)
*-oi(s), *-o:i(s)
e~ : *-eN(s), *-e:N, *-e~Ns
*-i:Ns, *-i~Ns
je~: *-jeN(s), *-je:N, *-je~Ns
*-ja:s, *-jãs, *-ja:Ns, *-jãNs
*-jo:Ns, *-jõNs
I : *-i(s), *-iN, *-i:N, *-i~N
*-e~N
jI : *-jas, *-jaN, *-jãN
*-jos, *-joN, *-jõN
*-je~N
i : *-iNs, *-i:(s), *-i~(s)
*-e~(s), *-ei(s), *-e:i(s), *-e~i(s)
*-aj
*-oj
ji : *-jai(s), *-jaj, *-ja:i(s), *-jãi(s), *-jaNs
*-je:(s), *-je~(s), *-jei(s), *-jej, *-je:i(s),
*-je~i(s), *-je:Ns
*-jõ(s), *-jo:s, *-joj, *-joi(s), *-jo:i(s),
*-jõi(s), *-joNs
U : *-u(s), *-uN, *-u:N, *-u~N
*-as, *-aN, *-ãN
*-os, *-oN, *-o:N, *-õN
y : *-a:s, *-ãs, *-aNs, *-a:Ns, *-ãNs
*-o:s, *-õs, *-oNs, *-o:Ns, *-õNs, *-õ, *-õis
u : *-au(s), *-a:u(s), *-ãu(s)
*-ou(s), *-o:u(s), *-õu(s), *-õi
ju : *-(j)eu(s), *-(j)e:u(s), *-(j)e~u(s)
*-jau(s), *-ja:u(s), *-jã(u)s
*-jõi, *-jou(s), *-jo:u(s), *-jõu(s)
=======================
Miguel Carrasquer Vidal
mcv@...