The have some american chassis' there and have thrown away all the worst bits:

Then they also have these two beauties - which I'd never before seen in the flesh:
...and some total madness tucked away in a corner:
So, as you can imagine, I was in my element (who of us wouldn't be!), but getting back on topic - for anyone here who doesn't know what the Muxsan board looks like, it's available here, and the gitsource is here. It's much the same as Damien's board on EVBMW. Naturally the link to the Muxsan kit there does not include their software to make the whole thing work, that comes with a slightly larger price tag, but still good value (IMO) for the ease that it provides.
In any case, the kit as provided from them looks like this:
So it's very tidy. It's just a 6-wire hookup. Ground is just a ring terminal to any bolt stud on the VCM, 12V comes with a fuse splitter which can be routed to the board at the left side end of the dash and sits nicely into the cabin lighting socket, and then the remaining 4 wires are the CAN ports which get soldered.
Finally then I enclosed mine in a little plastic enclosure that I had lying around and tucked it up behind the glove box.
Naturally, the box will need programming. The traffic from the battery needs to be captured for the battery ID challenge-response details (see the usual canmsgs workbook for the addressing etc..). These have to be taken from the battery bus, they don't appear at the ODB port. I used an Arduino MKR1010 + CAN shield, but you can also use the board itself to do the job. Send the codes over to Muxsan and they send back the appropriately configured HEX file for your install. The board is built around an XMega AVR which is programmed using a PDI interface. I used the Olimex AVR-ISP-MK2, setup as shown below (3.3v power active), along with Atmel Studio 7.
I did the CAN hardware install the evening before I did the battery swap, so my 24kWh pack was still in place. Dashboard before and after install is shown below:
Barring the regen and temperature readouts, it worked just fine - and I figured that if it wasn't compatible with the 24kWh battery I could just jumper the CANbus connectors to re-establish the original bus. Didn't need to in the end and the car never actually went into an immobilised or turtle state.
Everyone here is likely familiar with the battery swap procedure so no need to go into that bit, but the Yazaki connector is changed between the 11MY and 13MY+ cars, so that has to be revised. The respective pin outs are below, and it's almost exactly a pin-for-pin swap. If you've managed to get the newer yazaki connector from a Leaf and not an Evalia/NV200, it's very straightforward. The Evalia/NV200 has some redundant wires and the colour mappings are slightly more different. There are only one or two wire colour changes in the former case.
Once you've swapped over the Yazaki, it's just a case of plugging into the pack and taping up the redundant Heatpump port as shown below:
Body panels back on and car off the lift, the next startup looks like this:
and I can tell you - that's a feckin' great feeling to see those numbers on this chassis.

In the time since, the missus has been down and back to Tipperary town from here (Moyvalley), not taking it easy on the pack (so full motorway speeds for most of it), for the sake of a 20minute stop at Cashel and a few hours parked at the street charger in the town while she was visiting her Mum. That's a 340km round trip and the car ran flawlessly.
There's ~600km done in total since the swap and no issues from fully charged right down to low battery warning. Range estimation seems to track the usual ~20% high at full charge and is very linear in how it drops. I estimate the actual range under combined driving cycle conditions to be ~200km which is pretty much what I expected.
Given the mileage on my car I also refreshed the shocks at all corners, and pressed a new set of bushings into the swingarms.
The car is quite literally driving at least as well as the day it left the showroom 8 years ago, and with almost twice the original range.
Electrolytic capacitors notwithstanding, I expect to see 500000km before this battery is done. I'd be interested in any opinions regarding how long I should expect the power stages to last before those caps give out - might recondition a salvage drive and have it ready for fitting in that event depending on what the consensus is. The way I see it, they're about the only thing that's likely to cause any major issues over the next 5-8 years. Bearing wear I'll hear and correct as required, but there's not a hint of any of it yet.
Beyond that the next projects will likely be to update the interior to SVE spec, and parallel another charger to bring her to 6.7kW from the stock 3.6kW. Both as funds become available.
For any wondering, the recovered 24kWh pack is from a 131 registered 11MY (so the same pack) which I put in at 220000km with 30000km done. It's still strong apart from 1 weak cell pulling it down and will go on to refit a Vectrix VX-1 that I have here out of one half of it, and the rest is TBD. ...might try electrifying the ride-on lawnmower yet.

Anyways - hope the above is helpful/enlightening/encouraging... but above all I hope that it helps us keep these early Gen chassis on the road for a least 20 years.

*edit - per Kevin's request below have uploaded the most important pics direct to the thread.