You can make it work, but it may not be easy. Keep in mind that there are cheaper alternatives such as a smaller tank (hagen makes some VERY affordable 10 and 15 gallon tanks under $40) or even cheaper, a tub for $8. These options may not look as nice but will benefit your bp and cause less hassle for you.

If you have you heart set on the 40 gallon, my first question is how tall is it? If it is taller than 16 inches your bp has a good chance of pulling a "I am gona climb up the side and fall on my head 15 times a night"

You can put a divider in the tank if it is not too tall in addition to stuffing it full of plastic plants, but heating a tank that big is a royal pain in the arse (as well as keeping humidity up). I've made the mistake of using a tank too big several times and after all the greif, its just not worth it.