I have done it on a bike, 950 miles, and I wish I had access to a C5 on some of it!!
The hills in Scotland are not as bad as the ones in Devon and Cornwall, I would of thought 24V for the hills, and a support van charging the next battery is all you need-keep the weight to a minimum.
Apart from that the main problem is the posterior, ok on a saddle, but a C5 seat is not very ergonomic, perhaps a moulded pad fitting your needs would avoid the sore bits.
Remember lots of people have done it on recumbants.
Paul