Why not a Series Hybrid Engine Swap?

So, I've been thinking about this for a while. As some of you may know, I have an ongoing fascination (some might say obsession) with Full Size Jeeps (FSJs). That's the classic full size Wagoneers, Cherokees and Pickups built between 1962 and 1991. In my opinion, these are the original SUVs and they're damn near indestructible.

Unfortunately, they came with some engines that just don't cut in the modern world. Over the years, they came with an assortment of Buick, Kaiser and AMC engines. Now, don't get me wrong, there's nothing inherently wrong with any of these motors. At the time, they were competitive (well, except at the end), but, by today's standards, they're underpowered, inefficient or both.

Up to now, there's really only been two options...

1. Spend lots of money upgrading the existing drive train by adding things like fuel injection, headers and exhausts,  overdrive transmissions, etc. It's all possible and gives you the satisfaction of keeping the "soul" of your Jeep true to it's mutt roots.
   
2. Swap in a modern drive train from another vehicle. Traditionally, small block Chevy V8s have been a common choice for this, but the current range of LS and Vortec engines are about as easy and deliver a heck of lot of both efficiency and power for what's not a huge investment.

Now, I've spent a long time vacillating between these options. For me, I like the idea of having a "modern" AMC V8 with fuel injection and the like. On the other hand, the Vortec is a great truck engine, it mates up cleanly with a modern overdrive automatic and, perhaps most importantly, junkyards are full of them.

But because I'm always trying to figure out what an optimal solution could be, I'm thinking outside the box. I put together a list of things I'd want in a dream SUV.

• Off Road Performance
• Reliability
• On Road Performance
• Economy
• Comfort

Now, out of the box (or in it, if you like the wood grain tape) these FSJs do well off road and, modern features like automatic climate control notwithstanding, they're pretty comfortable. They aren't terribly reliable though (to be fair, the newest ones out there are 20 years old), they struggle to cruise at 75 and they might get 15 MPG downhill with a tailwind.

So, all that tedious set up aside, here's what I'm thinking...

Why not take a page from the diesel train locomotive book and do a series hybrid system?

Pros:

• Smaller diesel engine (such as a VW TDI) will provide ample power and, running at more consistent loads, will be ultra efficient and reliable.
• Electric motor has huge torque from zero RPM and can run at high speeds.
• No need for a traditional transmission, saving about 250 lbs.
• Supercapacitors can take the place of batteries, since they'll be used to bridge load variation between current engine output and electric motor needs, such as during acceleration or hill climbing, rather than for primary power storage.

Cons:

• Massive amounts of custom fabrication.
• Needs custom control systems and software to run said systems.
• Will still be a 20 plus year old vehicle with associated concerns.
• $$$$$$$

Now I'm guessing that's the main reason no one's done one of these already. I don't think any of the issues are insurmountable. Essentially, what I'm suggesting is a variation on what Fisker is doing with the Karma without the pesky "plug in" part that's great for being green but doesn't really add value to what I'm proposing. It's meaningfully different from the Chevy Volt because in my approach, there's absolutely no connection between the diesel engine and the drivetrain except for wires.

I'm not sure if this is something I'll ever get around to doing, but I thought I'd throw my hair brained idea out there. I'm open to suggestions and criticisms.