They have to set strict boundaries around each other, that it would be less... Creepy. A 16 year is still a kid, no matter what they might think. They cant really consent, not entirelly. By avoiding getting "intimate" and keeping an open door to break things off in case any of them change their mind(until Misumi finishes high school and start college, at least), Aizawa would be far less disturbed(and a lot of readers as well) by the idea of having a relationship with her BL goddess.
(I will repeat yet again: BL and GL/yuri are awesome)