Motorhead - system and mechanical design

I need to think about how I will house the Motorhead controls and integrate them with the generic MIG torch that was supplied with the Arc Captain welder. I also need to supply some power to the controller, ideally from the welder end of the cable.

Mangling the MIG torch:
Here's what we've got:

Comes apart easily enough:

The gas comes down the main "pipe", with the electrical power coming down the outer braid. Then there's a pair of wires for the trigger switch:

The other end has a generic Euro connector, which takes care of the gas, power and trigger connections in a quick connect connector system.

It also comes apart easily enough. 

The trigger wires are routed alongside the power braid, not inside the pipe itself.

The MIG wire comes along this Bowden cable:

The trigger "switch" is little more than a washer that shorts across a couple of simple spring loaded contacts.

So, I guess I need to insert the normally open Motorhead relay contacts in series with the torch trigger switch. For this, I will use a 3.5mm mono jack socket, the sort with the in-built switch that will leave the trigger switch operational with nothing plugged in - but will put the external switch in series when the plug is inserted. That way, the torch will work fine without the Motorhead but will assume Motorhead powers when plugged in. If you see what I mean.

I've ordered some Chinesium 3.5mm sockets. I will fit one of these into the MIG torch housing.

PCBA housing and interconnections:

Meanwhile, the Motorhead PCBA needs some sort of housing and some interconnections to the welder.

Here's the Oriental Motor (Japanese - but made in China of course)

The MIG cable is marked with a part number but I couldn't find any information on the internet. No problem, these torches are cheap as chips, so if I need to get another one to butcher it's not a major outlay.

Anyway. Over to Fusion 360. Here's the imported PCBA positioned magically in mid air, roughly where I imagine it needs to be in the final assembly:

And with a simple box-like housing, it's looking a little more like a workable concept. The dimensions are taken from the NEMA37 motor, so that the housing will sit neatly on top, flush with the sides. I won't win any industrial design prizes for stuff like this but for now it's a start:

Right - let's make one of these things. It's not a finished design by any means but I want to get on and try the thing out before getting too far ahead of myself.

Looks OK:

And not surprisingly, the PCBA fits inside nicely:

With some double sided foam tape, it becomes one with the existing motorised head:

Now to sort out matters "at the other end of the cable"...