Yeah somewhere along the way the term "bioactive" seems to get confused for "add cleanup crew and never clean the enclosure", the whole cycle isn't going to work unless you have all the elements there. Without plant material (particularly decomposing plant material) and fungus, the isopods won't have anything to eat, and the issue with snake waste has already been mentioned. Isopods and springtails also breathe through gills, so they need to be kept in quite damp substrate to survive - if it dries out they'll all die.
eta: without plants and other rotting material you'd need to be feeding the isopods, and they prefer to ignore things like apples and carrots until they're actively decomposing, which would mean the snake is in there hanging out with rotting food. My isopod-only enclosure is honestly pretty gross, I wouldn't want to expose other critters to it.
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