For starters, I'd use a trusted, verified thermometer to check what the actual lowest temp is that the smoker will run at,. It may run cooler than the advertised low temp setting, and it would not surprise me if you reported back that it does in fact run at lower temps. Ambient temps can and do effect electric smoke chamber temps, too, so it may run cooler on cold days. If it doesn't run low enough, then it's time to devise a plan to make it do what you want.
Just a couple ideas I had rolling around in my noggin after reading your post. If the smoker has a digital controller, then it needs power all the time for the temp probes and readouts to function properly. If it is a older analog unit, then it has a thermostat which can be bypassed with an aftermarket modification by simply installing a thermostat to take over the OEM thermostat's job. Swap out thermostats, wire it in on the same terminals, install the control knob and wiring and you're there. You just need one that can be adjusted and runs within the temp range you'll smoke at, and, be capable of handling the power consumption of the heater element or be coupled with a relay to handle the power to the heater. You should be able to find these items online...probably
Amazon, and possibly elsewhere.
If the smoker has a digital controller, then you would bypass the controller's output to the heater element, just the same as the analog. You may need to set the controller on a high temp so it has power to the thermostat at all times. Or, you'd run power from the main terminals to the thermostat you're installing to power the heater, as well as to the controller for temp probes, if you wanted to use them. By not bypassing the entire controller you will not loose the functionality of the OEM smoke chamber and meat probes, if they are installed and in working order. In the event that there was firmware installed in the digital controller which caused a fault to be displayed when the heater element was disconnected (as it would be if being bypassed by your mod), then you may not be able to use the probe temp readings after all...that part I'm not sure about with the digital MES.
OK, just read back, you said no windows so I'm assuming that is an older analog MES...that simplifies things a bit for the mod.
One side note: the MES may not provide sufficient smoke at low temps on it's own and a separate smoke generator may be needed. Seems that others have mentioned this in the past (I don't use one, so I'm just relying on memory here).
There are a multitude of ways to create an external or internal auxiliary source for smoke, and there are pre-manufactured smoke generators to be had...different types and models depending on what you want to do.
Hopefully other MES owners will weigh-in with their thoughts...take it from here guys.
Eric