Alex. If you aim for 5C it is possible to stay out of the condensation/icing range, unless the humidity is particularly high. A degree or two makes a big difference. I found 7C a good compromise on dewy nights with an earlier prototype.
With 10C and 5C as presets or ball park depending on humidity, the results will be quite OK. No need for complex power scheduling to a heater. Having said that an argon bag will let you go subzero, no problems. I just find the heater convenient for the time being.
Perhaps we should write up a detailed step by step. I have some rough notes. Guidance - pick what you want out of it. Glen may want to add to the pool and suggest improvements. This should get you started.
Here and
Here