The heater thing makes sense in the winter. I need heat anyway but summer will soon be on us and we will be loosing it. In fact may have to get rid of it.
As for the witness thing I am not sure if it would or not. I am looking to move my existing server I host clients on to new provider. convert it from a vps to a cloud system with sever virtual servers. One for the existing hosing system, two for the witness servers. To provide this in two hosted site would currently be about 50 SD each. I think I could do all three for the same price. I already pay 65 Canadian for just my hosting service. So I would be converting from cnd to SD. Know that the usage is low to start and ramps up so I don't need vast resources to start.
Down in NZ so just hitting winter here. Yep, summer I plan on moving the rig to a cooler room we do not use. As long as it covers the power costs then running through summer is not an issue for me unless I have to run extra cooling. For mid summer it might need to be powered down when the ambient temp is too high which would effect ROI. If it can pay the parts in say 9 months then it is viable imho.