My personal preference in cases like this one is always the same: never disconnect an important service from the main hub, unless you can provide a comparable alternative, which Belfiore isn’t. If capacity in the S.M.N approaches dictates that through trains need separate through tracks, then that might be argued even for just 4 tph (in each direction). If capacity is not an issue, it depends on how much money a time saving of 5-10 minutes is worth the Italian taxpayer - not going to judge here.
I think I've got it.
Milan - Rome services are straightforward. Given the 4tph non-stop through services, Milan - Florence and Florence - Rome can operate as standalone services.
Venice - hourly service to Florence; then in the opposite hour have Venice - Bologna and Verona - Bologna services meeting at Bologna at the same time, cross platform interchange, and alternate which service goes to Florence and which goes to Rome. Operate additional Florence - Rome shuttles according to demand.
Firenze S.M.N then operates as a pure turnaround station (no reversals) and build a new bypass line for the non-stop services.
This would require cross-operator ticketing and probably running Italy's high-speed services as commercial PSOs (PSOs which pay the government money, which I believe isn't incompatible with the 4th Rail Package).
Anyway, Belfiore is being built and they'll have to work with it.
