Hey Dr del has some good points but for me personally I have an enclosure that is 24 inch by 24 inch and 18 tall. Keeping the temps correct isn't really very hard but the humidly is a it trickier. It can be done however, substrate choice and a few tricks here and there.
3 feet tall might pose a bit more issues with heating and humidity. My guy climbs quite a lot in the nights, Many well know authors also back this up,
Bartlett & Bartlett "despite being heavy bodied, ball pythons can climb adeptly."
de Vosjoli "...may even climb on branches close to the ground"
Personally a larger enclosure like what you have suggested is fine (less height maybe easier...) Lots of 'landscaping hides and plants will give a secure feeling for your ball and give you something to look at when it is hiding.
There is nothing wrong with tubs! They are easy and simple to keep and the animals are healthy kept in tubs. That is why breeders use them!
I have one snake and one coming so it takes me 20 min to clean his enclosure (40 for two) I enjoy that time. It is a bit more of a of a balancing act to get things right I love technical issues anyway. I also relax after work by just looking in the enclosure sometimes my guy is out in the evenings sometimes not, but either way I enjoy that too. I can see his trails he makes and I enjoy the enclosure look too.
Personally it is worth the extra work. I had him in tubs and I felt like I wanted to take him out all the time to handle as I couldn't see him through the sides. Than can cause stress so in my case a bigger display enclosure I get my time with him with out over handling. Just my personally feelings here.
My biggest trick for humidity is rocks. I have a chunk of a fine grained porous rock (rainbow stone in my case) I actually have two... I soak one for a day and them pat the surface dry and place it in the enclosure. over a few days it dries out releasing the water it holds back to the air. It takes 3-5 days to dry completely and bumps up the humidity a notch (7-10%) Then when it is dry I place my second one in taking the first out and into boiling water from the kettle and start the cycle all over.