looks like the gang has you covered. first off, termites and ants are bad. and i'm not even thinking about the viv. just imagine, if, for some unknown reason, one or both of those cultures were to fall over during the night. eghads!! now, not only your living space will get them, so will neighbors (if you have any), and more importantly, you just may have introduced a potentially catastrophic invasive species into your local eco system, because they will get out, make no mistake of that.

snails are just not a good thing in a viv. although aquatics in a water feature are fine. and there is rarely a such thing as "one snail" lol

as far as carnivorous plants go. they won't eat the amount of leftover food you think they may. they also do not like the nutrient rich soil that we use. in some species, it would actually cause their demise. humidity wouldn't be an issue with BB toads, as much as it would be in a dart tank. ventilation wouldn't be an issue either. you could possibly keep a drosera species in there (sundew). a bladderwort like utricularia gramminifolia (UG in the aquatic planted tank hobby) would also be a viable candidate, if you could get some, and it would have to be planted on the margin. you could even get away with one of the short, low growing sarracenia species, but they would probably grow too wide for the tank. i can probably come up with a few others, but my mind is drawing a blank right now. as amy mentioned also, some carnivores are very delicate. i know my D. Filliformis is ridiculously fragile, so i would worry about even the smallest toad trampling it to death.