How it will affect the linguistic history of the Italian peninsula?
If the literary language reflect changes in everyday speech, then pretty similar to OTL Italian except maybe more conservative spelling, eg. Victorio for Vittorio, Caesare for Cesare, and Julio for Giulio.
If a lingually conservative literati is retained like in China, changes may be more limited, but these may still occur as IOTL in the literal Latin:
- Merge of vocative to nominative and ablative to dative, functions remain separated by using prepositions.
- Articles emerges.
- Deponent verbs regularized into their active forms.
- Cardinal numbers no longer decline, but
unus "one" might retain its declension when used as a pronoun.
- Progressive voice appears.
And wild guesses in vernacular Latin:
- Further disintegration of cases into nominative and oblique or totally disappear like IOTL, replaced by deliberate preposition, and word order shifts to SVO from SOV.
- Passive voice replaced by
esse "to be" + active voice.
- Future tense replaced by infinitive +
habere "to have" due to consonant shift of Vulgar Latin making the preterite and future homophones, this may or may not influence the written language.