Wow! That's impressive navigation. In theory, it looks doable, but I have no first-hand experience with anything between the end of the Cinque Terre in Italy and Oleron St-Marie in France.
Some suggestions / questions:
1. Are you planning to skip the Pistoia - Lucca section? The Cammino di San Jacopo does connect the two places, and it has (what appears to be) a very useful website, referenced in my post #6, above.
2. Looks like your route on the Cammino Della Costa avoids Cinque Terre completely. Given the crowds there in summer, that's probably a good thing. And I see you've found the guidebooks published by Terre di Mezzo, which are quite helpful.
3. It also looks like most of your route along the southern coast of France avoids going through the big cities, but if you're worried about accommodations in the bigger cities, you could simply check a site like booking.com to see what's available tomorrow. That will give you a sense of availability in general. For example, checking Nice for tomorrow night -- a Saturday -- shows nothing in the way of inexpensive hotels, but quite a few hostels where you can get a bed for around $50 American. (I have no idea what your budget is, of course).
4. If you're worried about time pressures, you could consider skipping the section across southern France, which seems to have the least walkers' infrastructure. Of course, I have no personal familiarity with this stretch, and you might want to check out some of the blogs of the people who have walked the Via Aurelia and / or the Cammino della Costa.
5. When you get to Oleron St. Marie, you might consider staying on the Camino de Arles, instead of heading over to St. Jean Pied de Port and the start of the
Camino Frances. The Arles route turns into the Camino Aragones at the Somport pass, which is the border with Spain, and joins the
Camino Frances just past Pamplona. (if you want to go into Pamplona itself, mapy.cz will show you a cut-off that will take you there from near the end of the Aragonese). The Arles / Aragones route will give you a much more tranquil entry into Spain than going via St. Jean Pied de Port, and IMHO, it's a much more beautiful traverse of the Pyrenees. There's also plenty of pilgrim infrastructure on the Arles - Aragones combo, and you won't have to fight for a bed as you will along the first few stages of the Frances.
6. If you find the Frances too crowded for your taste, you could cut off it at Ponferrada and follow the Camino Invierno into Santiago. The last 100 kilometers on the Frances, from Sarria onwards, will be incredibly crowded, so this gives you an alternative. Of course, you may welcome the company!
7. The Spanish web-site, gronze.com, is a terrific source for information, especially on available, pilgrim -friendly accommodations. It has sections covering the Via Francigena, the Arles router, and all the possibile caminos you'll follow in Spain
That's my 2 cents for the day! You've enabled me to avoid doing any planning for my own camino coming up in September. I definitely find it more fun to plan someone else's life than my own.