Southern Spain would be nice now, far too hot in June July August and Scandinavia far too cold in the winter making it impossible.
Re charging. I'm looking at the Goal Zero Nomad 20 solar panels and their Sherpa 100 battery pack. The solar panels will fit nicely over the rear panniers and the charger can be mains charged and has multiple inputs and outputs. It can charge smartphones, i-pads, AA and dslr batteries, laptops. With your Son 28 front hub I would consider a Tout Terrain head set USB plug as well so you have two different sources of power.
Rohloff hub 36 holes is seriously heavy duty. It is my preferred choice as well. 36H wheels will mean you will be able to carry some serious weight. Maybe worth carrying a spare Rohloff rear sprocket or two or indeed different sizes, for climbing and the flat. Also you'll need to carry the hub oil change kit. You won't have any problems in Germany ……...
Tents - I have looked long and hard and there are many candidates, but the one that stands head and shoulders above the rest is the MSR Hubba Hubba.
If doing Northern countries in winter you need a good sleeping bag at least a 4 season down bag. But the winter cold can be unremitting and you'll have problems staying dry and keeping your clothing dry. I can't think of anything worse than putting on smelly damp/wet cycle clothing on a cold winter's morning with the prospect of a long cold ride ahead.
Exped mats may be comfortable but they are pretty heavy and large. I have a 3.8cm Mountain Equipment one which is very comfortable.
Panniers - 4 all round with a bar bag, either Ortlieb or Vaude. My preference is for Vaude as they are just better.
Tyres and tubes - I would go with a couple of spares of each, tyres folding. But in Europe you are never going to be far from a good bike shop or indeed internet to order some from UK.
Pump - Topeak Road Morph for MTBs as larger volume.
Stove - Trangia 25-6 running on gas. Self contained having everything - you can cook in and eat out of the pots. Butane/propane gas is available in most major European countries even France however a little more difficult to find there as the French prefer Camping Gaz still thinking they are right on everything and the rest of the world will do as them. Also MSR are just about to launch their new WIndbolier stove which is pretty impressive. Similar to a Jetboil but boils water so much more quickly and is resistant to wind as it has a neat convector wind shield.
Don't forget water carrying capacity - 3 bottle cages and separate bladders.
Lights just in case, your usual lights will be fine, no need to get anything special. Definitely a head torch - Petzl.
Clothing - wet weather gear and over shoes as it will rain.
GPS/Phone - MemoryMap have just launched the TX3 unit which is a GPS combined with Smartphone. It comes with 1:50k or 1:25k OS mapping for UK. It uses Seal smartphone which few have heard of but watch this space, as soon as a large manufacturer decides it is the way to go, GPS and Smartphones will seamlessly become one.
Kindle to avoid taking heavy books.
Net book or small lap top for editing pictures, keeping journal/blog , etc.
Camera and or head cam such as a Go-Pro.
An itinery of places you want to go and things you want to do. It would be very dull if all you did was ride from A to B everyday, well it would be for me. For instance maybe you might want to do some walking, hiking at some point, as I am guessing your tour is as much of a holiday as it is a bike ride. Maybe you could have a theme to your ride to make it more interesting?
This is it for now.
HTH.
