There is nothing wrong with getting a good thermostat for your snake, breeding or not. In fact it is far preferred to do it the right way, and VE makes good thermostats. I have 5 or 6 of the VE300X2's now and they work great. You buy that VE300 and you have a good thermostat no matter what. Even if you change your mind later and start breeding or increasing the size of your collection, you have a solid thermostat to use somewhere in your setup.
I'm a fan of getting 1 enclosure for the lifetime of the snake, as well. If it's too big or he seems uncomfortable it's fairly easy to fill it up with stuff to make him more secure.
I don't have a lot of experience lately with aquariums, so I can't help with heat and humid issues in them. I can say you might want to consider getting a PVC enclosure if you want a display enclosure. Something like the T8 from animal plastics: http://www.apcages.com/home/terrestrial/T8/T8.htm
Heat and humidity are much easier to manage in that than an aquarium.