I’m working on a custom setup which is a really early version. It’s working stable at home though.
You can see the SmartApp here https://github.com/anderssv/smartthings-code/blob/master/smartapps/smartthings-f12-no/heating-control.src/heating-control.groovy . You can test if you want to, but remember to install the thermostat device handler from the same repo. 
I also recently saw this setup (but I think it requires real thermostat devices), that I’ve been wanting to test. [BETA RELEASE] Multi-feature Programmable Thermostat SmartApp
Let me know if you test mine and have any quesitons, but do it in PM or a new thread so we don’t hijack this one.