Off-topic but why the support vowel after the s? Is it an internal development or Italian influence?
I don't think it's Italian influence – rather, all Romance varieties south of la Spezia-Rimini line that preserve final obstruents (such as
-s/-t) exhibit a support vowel after it. This is therefore a repair mechanism in the face of a prohibition on obstruents ending a syllable. The other repair strategy was their assimilation with further morphosyntactic reanalysis, as in most of the Italian area, where it's become limited to stressed syllables and to certain monosyllables (
raddoppiamento fonosintattico). This makes the prohibition look very old, and the repair strategies inherited, or at least somehow independently pre-determined as soon as the prohibition arises.
Since Sardinian exhibits the most original stage in the development of the
raddoppiamento (which is integrated into its system of lenition and effectively blocks it), it's reasonable to think that the support vowel situation is also original, and hence in the parent variety of Late Latin assimilation and vowel insertion were alternative or complementary (just as in Sardinian) repair mechanisms in a system of sandhi similar to that of Sanskrit. There (still hopefully) are varieties around Cosenza and southern Lucania that preserve final obstruents, though they seem to use schwa or /i/ as a support vowel instead of copying it as Sardinian does. The now-intervocalic final /t/ is voiced in some of them, just like in almost all of Sardinian.
I'm not sure how original this is, but many modern (chiefly southern it seems) Indian pronunciations of Sanskrit insert a phrase-final copy vowel even after the coda /s/ undergoes sandhi to become [ h ] (known as
visarga, spelled : and transliterated ḥ), which then voices to [ɦ]. This is in effect a combination of these two repair strategies, but may be due to a newly-arisen ban on coda [ h ] which is itself the repair outcome of a ban on coda [ s ].