I think the controller you're looking at, Dr K, will work as TallBM described.
The only real drawback I see with it is that you will no longer have a thermostat. Instead, you'll just be adjusting the power to the heating element directly yourself with the knob. So you'll have to constantly monitor the temperature in the smoker and adjust the power to the heating element yourself.
I've gotten spoiled by the MES, and I like to be able to set the temperature of the smoker, then walk away from it and have a thermostat maintain the temperature I've set. So that's one of the main things I really like about these electric smokers versus (in my case) the charcoal unit I have. However, if you'll be tending the smoker during the run anyhow, then the control you'll looking at would likely work just fine. It won't be any different than running a charcoal or gas smoker in that regard, and really, the charcoal unit of mine has worked just fine.
You'll probably get a good feel for what settings of the knob work the best for different meats and weather conditions just like we do when running a charcoal unit. But it will be a lot easier for you to adjust the power than it is with a charcoal smoker.
I'd do like TallBM suggested and use a three-wire power cord. Use the hot and neutral to power the heating element, but wire it so that the snap-disk thermal cut-off device is still in that circuit. Then connect a good ground from the chassis of the smoker to the grounding wire of that three wire cord. Then the ground pin of the controller will carry that ground through to the ground of the receptacle into which the controller is plugged. That way, the controller and the smoker will both be grounded.
I like the idea of a sleeve between the inside of the smoker and the outer wall to seal things off from the insulation space. It would be good to keep moisture and smoke out of that space, I think!
Maybe a guy could use some high temperature RTV to seal both sides (or at least the inside end) of the sleeve tube. But the tapered pen casing might work great just by itself because you could push it into the hole from the inside until it jams in place and makes a seal to the inside wall of the smoker. I'm going to want to do the same thing for mine. I don't like the idea of condensation forming in the insulation space. I want a "vapor barrier" like you'd install in the walls of a house or building, I guess! :)
I found out Opto 22 has an app for Android or IOS devices to let you access various things over a WiFi network to which the controllers and I/O are connected. I just played with it, and it works great, but I'll have to use one of their newer Snap PAC controllers to have access to the "Strategy Tags". The older model controller I tried this with lets me look at I/O, and control it as well, but it would be more convenient to be able to adjust variables, tables, etc., in the running strategy, and the older controllers don't know how to do that. I've got newer controllers laying around, so I'll use one of those and try that out when I get the chance.
I was thinking I'd need to use a laptop or other PC connected to the network to adjust and monitor things, but this little app, running on a tablet or phone will do everything I'd really need, too, so that'll be cool.
They've got a full-blown system for remote access to their systems that lets you create very user-friendly Man Machine Interfaces to run on phones or tablets, and connect from anywhere that you have internet access, but they actually want real money for that setup!
Being a cheapskate, I want to do this all with bits and pieces I already have laying around and with their free software. This app was just $5, so that's acceptable, I guess.
Woo Hoo! I can see the temperature in my office now from anywhere my WiFi reaches, and I can turn a light on and off as well as adjust the duty cycles of some Time Period Outputs. Yee Haw! (It doesn't take much to amuse a nerd, I guess) ;)
When I get the new style controller set up and configured, I will be able to adjust variables within a running strategy from my phone or tablet, which will let me adjust setpoints and such. There are ways to let this work over the internet, too, but I'm not sure that's really necessary since I'd at least be somewhere around the house while smoking stuff. Just being able to monitor and control things from an easy chair or the like without needing to go out in the cold is nice. That's one of the features I've always liked about the MES (and similar smokers). So it will be nice not to lose that feature.
And that looks like one of the nice features of the system you're using, too. Remote control and monitoring is nice. I'm thoroughly spoiled.