When someone is able to build an trailer with electro engine for using it as 6x6 (2x together with 4x4) for the real bad passages - this would be nice
But back 2 topic ;-)
Do you wan`t to use the car as dailydriver in europe, does it have to fit in underground garages and so on?
You can look @ my Blog for an sample as full Dailydriver & Travel simultaneous requirement. I would do it the same way again for this dual purpose.
When you have the space for an additional "travel car" (or don't have to use city parkings) - you have many many options to discuss:
I have listed some solutions here:
Trans-Africa: Welches Fahrzeug?
Maybe you should look also beyond your favorite brand ;-)
And never forget, that you can do near any trip cheap with any good 4x4 and a simple tent and some basic equipment. So don't exceed your "buildup cost" when you are on budget ;-)
And keep your weight so low you can - to avoid breakdowns abroad (and the legal stuff in europe).
I also like the trailer solutions who are available - and when you search in youtube "gall boys" you will see that you can do much which a trailer behind. But it is a limitation, specially if you like to drive abroad..
A trailer could also be a pain on the small dirt tracks in the europe alps - which the growing traffic because all years more roads get closed.
Surfy