Yes, i've got rangy seats in my 100", very comfy and have got arm rest's as well, in the near future i'll be changing them to heated leather ones B)
As for getting to the battery, i can't as they seats are bolted to the box. I've wired in a quick connect jump lead, and fitted shut off switches very close the the battery. The battery can be totaly isolated from underneath by undoing the earth bolt on the chassis.