[Mark7]

I like your way of thinking... and your idea. I have the same issue and complaints about my bedroom A/C. I did research a kit made by the manufacturer of the unit (I think) or someone making it for that unit that was a plug and play deal for a LV thermostat, but it was expensive and I don't full time so I turned my attention to other mods and let that one go.

One observation... since you will be building something to house the relays with LV coils, why don't you just include a 24VAC transformer and use 24 VAC coils (Relays) since that is exactly what most LV thermostats are looking for, of you use a digital or programmable model.

I did change my main A/C to a residential / programmable thermostat to get away from the temperature swings, but the one I used has a couple of AA batteries in it that run the board and the relays that all for heat, cool, or fan. It really worked out well after I figured the fan only thing out.

Looking forward to seeing your eventual setup!