The 17 qt tub is just fine to put her in while you are cleaning. You don't need to put a UTH under it, she will be ok. If you are spot cleaning as necessary, you really don't need to deep clean all that often. I find that doing some minor cleaning frequently is much better than waiting, and having to do a major clean.
I really wouldn't worry about having to put her in the tub permanently. Your enclosure looks pretty ideal. Seems like your temps and humidity are good. Definitely a ton of hiding spots and cover for her. Let her settle in for a significant amount of time before deciding on any other kind of enclosure. Even if she doesn't eat the first couple weeks let her be. A perfect enclosure takes time to get used to for a baby bp. These snakes are super prone to stress, so just be patient.
If you enjoy snake ownership, definitely think about a BCI! I transitioned to have mostly BCIs and I think they are wonderful. They are hardy, usually easy going, and don't have nearly as many stress and feeding issues. If you can accommodate their size, which in my opinion is very manageable, you will have a great pet.