You have selected the worst form of transport...
I'm very sorry, but even if you were sat next to me, I couldn't guarantee what the temperature would be. It doesn't really matter which aircraft you are in although bigger is better as they have a greater thermal inertia. In reality, there are too many variables which may result in you experiencing a temperature which could cause you irreversible injury. The ideal temperature would be 22˚C for everybody but regularly I find that I'm unable to control the temperature to my satisfaction, let alone the passengers. Therefore, if I was asked by my company if we could absolutely guarantee a temperature I'd say I couldn't and also if asked whether we should accept a booking, I'd suggest that we decline to offer you a seat unless you indemnify us.
PM