glass tanks can work, if the top is closed and airflow is reduced.

ive seen many good glass terrariums, these have glass on all 6 sides and sliding or hinged doors at the front. these can keep the humidity quite well. if you have essentially an aquarium with no top and glass on 5 sides, i guess you just need some sort of top for it.

also, too big is not really a problem as long as you put in enough fake plants and hides. sometimes snakes feel unsecure in large open spaces, but if you add enough fake plants and hides and maybe cover up the sides, that should solve the problem.