Oh wow! This is awesome! Thank you so much - this is very helpful!
When I saw your proposed (wild and crazy) journey, I put together that itinerary mostly for fun, not thinking anyone would really follow it.
BUT -- if you're really serious about it, I think it's readily doable, along the caminos I outlined, at least up to Sarzana on the Via Francigena. After that, however, I'm not sure I'd follow the hodgepodge of trails across the Apennines suggested by mapy.cz because there doesn't seem to be much in the way of services and places to stay.
Instead, if I were doing this wild journey myself, I'd probably elect to stay on the Via Francigena from Sarzana down to Lucca (awesome, wonderful small city by itself). At that point, I'd veer off onto the Cammino di San Jacopo over to Pistoia -- plainly shown on mapy.cz -- and from Pistoia I'd take the newly-marked Via Francesca della Sambuca. Here's a website, in English, devoted to it:
https://www.discoveraltorenoterme.it/the-via-francesca-della-sambuca/ Mapy.cz does not specifically label the route as the Via Sambuca, but it can easily be traced on it (or the tracking app. of your choice). Looks like you could also stay on the Cammino di San Jacopo past Pistoia and, a little north of Prato, you'd run into the Via della Lana e della Seta, which would take you directly into Bologna as well.
A further alternative for traversing the Apennines -- if you're not wedded to every f'ing inch -- would be to take the train from Lucca to Florence -- then picking up the Via degli Dei from Florence to Bologna, which is a wonderful and well-supported trail.
If you really undertake this journey, you MUST let us know how it went.