LOL I was not planning on mounting the yellow bucket... but now that you mention it........

Roof rack most definitely. A dd some KC Daylighters for illumination, and a jerrycan mount on the roof, it allows you to fuel by gravity feed without taking it down. If you cover the rear and side windows with tubular steel and wire mesh, it will protect the glass from 'zombies' and allow you to hang rucks from the roof rack, freeing up more room up there for gear. Add some 31's (BFG TA KO's are my preferred tires).
My experience with Discos has always been second hand. My neighbor had one he called the Valdeze after the head gasket blew, oil everywhere. Also he had to rewire the truck as British electrical systems always seem to cause issues (it's not rocket science guys). If you add a winch, get one with a tubular mount, so you can put the winch on either the front of rear, it beats having to run cable under the vehicle. Just my $0.02 worth.

The problem I have with Land Rovers are: they are made in England. My experience with Land Rovers is that the transmission fails right at the start of hunting season; The dealers can't get parts in a timely fashion; The wipers don't work when it rains. Probably why they are so popular in Africa. Get a GMC 1500 Crew cab with Short box, gasoline powered, Work Truck, PU; If you get an older one, you can convert the engine to a Pantone Reactor for a few hundred dollars and get 80 mpg. Then you haver enough room for friends, and ammo. Last for 300,000 miles. Hummers are now made in China, so they are out.
Relying on an English vehicle in an emergency would not be the best idea in my estimation.

Welcome to the LandRover club. As the proud but broke owner of a 2004 Discovery II, I can only say I hope you have a high tolerance for what can only lovingly be described as "idiosyncracies".

Oh, and the kitty litter in the yellow bucket will come in handy for the fluids leaking out of the thing.