If we are being constructive about the conversion rather than dismissing it I would not be looking at pure plug in EV. I know this may defeat the point of what you are trying to achieve but for all the reasons above, especially off road and towing pure plug in EV is not practical for a defender. I would not be looking at hybrid drive either as you do not really get any benefit. I would be looking at electric drive with onboard generator if I was looking to convert a defender to Electric. This is the principle that trains use and is one of the ways people are looking at converting HGV's to electric. This also ties in with my comment earlier about treating a defender as a light truck not as a car.Heh, I bet you donned your asbestos undies before posting this thread.
I'm in a small minority in that I like and own Landrovers but also have a small ev that the wife mostly uses for nipping to town and to keep the wear off more fun cars (Seat Mii) and its ok. But a 90? Kind of defeats the utilitarian aspect so I'm with the other peasants holding pitchforks.
Being constructive, the things I would consider about my 90 if I had to ev'd it are really to do with how the conversion has been done.
You have to do a electric heater conversion anyway so a improved one with ac that can be directed to cabin heat or just clear the windscreen while your fixing your wet knee issue, and also fit heated seats because running the cabin heating on the ev kills its range in winter when battery chemistry alters characteristics because of the lower temps, but you don't need full cabin heat once off "shore power" with heated seats unless the journey is very long and its extremely cold. I can drive our little ev for its full (reduced) range in winter with just the seat heating in minus temperatures.
Range and cold weather issues are also what I would be most focused on finding out if I was a purchaser, as when its snowing I want to use my 90 instead of the other car because its more suited the conditions, but if battery chemistry means I'm not going to make the journey comfortably or while towing a big trailer it defeats the point of it and I might as well take a "normal" car.
I'd want to know what towing a load does to range too in advance. No I'm not stupid, I know its going to be bad, but I need to know how bad to know how usable it will actually be and work around it.
Weight is also a big factor, the base vehicle is not exactly light to start with, and I can't see it not being even more lardy and having any usable range in cold weather in this respect.
I'd also consider offering a option to slow recharge/recover it when it inevitably runs out of charge offroad or somewhere awkward. This sounds like a tongue in cheek dig but its based on practical experience as we live out in the middle of nowhere, a couple of times I've had that "I'm trying to limp home, but get the granny charger & the genny loaded ready in case I don't make it" call from the wife mid winter.
Small points, but from practical experience they're what I'd use to assess any converted vehicles on amongst other criteria.
I follow these guys on youtube but this is their main website: www.edisonmotors.ca. They are in the process of making an electric logging truck for the Canadian wilderness. This sort of approach I would suggest is far more in keeping with the spirit and general usage of a defender than trying to look at electric road cars. It is a pure electric drive with a battery pack. It has the ability to run purely on electric and be charged form a plug in charger. But it has an onboard diesel engine attached to a generator to recharge the batteries while driving if required.