Kat, I had a great time, thank you. Pau, Lourdes, Oloron Ste Marie, Somport, Jaca, and joined the Frances at Puenta la Reina. I continued to Estella intending to get a train home from Pamplona or Logroño but in the end cycled to Andoain (is on the Basque Camino) on a really good route given to me by the owner of the Albergue I stayed at. First half is to Latasa via Puenta la Reina and Extauri and Irutzun ( which has two hotels) only one real climb, then mostly along the river, all on quiet roads. The real treat is the second part on a Greenway which was a mountain railway, and which is downhill ALL THE WAY for over 60 km to Andoain. It does go through several tunnels, which are lit, but not very well. One is nearly 3km. There are some fantastic views and a couple of places to eat. Andoain to Hendaye was supposed to be on the train but it broke down half way so I cycled the rest of it.
I took several diversions and extra bits, a lot easier with the assistance. I never actually ran the battery flat except Somport, although I once got a top up while eating lunch, which probably wasn't necessary.
I met a couple of Dutch cyclists using ebikes who carried a second battery each. I was fine on one but it's new. My bike has a range of at least 120 km on the flat. It's a Swiss Flyer Upstreet 4. Most days I did 60 to 80 and used about 60% to 75%.
I think you need to take a fast charger and a three way adapter so you don't monopolise the sockets where you are staying. I usually charged the battery in the room as most places don't have power in the bike garage. You will be carrying more weight than on a normal bike (battery, motor, charger and adapter/extension lead) as well as the heavier frame that an ebike usually has. Also if you have a hub motor you will need more tools if you get a puncture, so I strongly advise Kevlar reinforced tyres. You can get special tubes that are like a sausage, so you don't have to take the wheel off. I own one for another bike and suspect it will give a lumpy ride. Plus they are expensive. I took my electric pump, two spare tubes, tyre levers, a few spanners and Allen keys, CO2 pump and spare gas cartridges (they will take a big bike tyre to 2 bar) chain splitter, spoke key, oil, some gorilla tape and webbing straps (stops the bike falling over on trains etc) Lock and cable. I normally leave the panniers locked on the bike and just take out the inner drybags unless the bike has to be outside at night. I have 8kg clothes, phone, tiny gas stove and sleeping bag etc. 2 litre imitation camelbak which also holds passport, money, ereader and credential etc. About 3kg for that. I took waterproofs, no cold weather gear so add a bit for winter. Camping add some more depending on your requirements for comfort.
All this means good battery management as otherwise is hard work. The gears don't cover the same range as a normal bike. There isn't a serious granny gear on most, as you are expected to use the assist. Logical. I have ten gears, many have fewer. I averaged 15kph most days and never had to push the bike. My last bike Camino I was a lot slower. It is significantly less tiring, and quite a bit faster. On the whole I can go further and arrive fresher. It isn't a free ride, but yes, as you would expect, it is easier. Just as walking pilgrims find baggage services a help....
Oh, and no punctures. That's a first for me.
To sum up. It's entirely feasible. I didn't meet anyone who showed me any disapproval or was rude about me, at least to my face. Quite a few people had a go. I'll be doing it again, DV.