I don't know anything about sealing wood (or particle board or whatever) so I'll let someone else answer that one. But the main question that comes to mind for me is this: If you take that center divider out, will the piece be able to maintain its structural integrity? That divider could very well be helping to not only hold the top up and keep it from bowing down (and even the tiniest bit of bowing would ruin the slide on those glass doors), but also may be integral in keeping the unit "square".
If you're sure that center piece is just there for aesthetics or simply to support the weight of a TV, or if you can figure out some structural substitute that won't compromise the integrity of the piece (maybe cut a big hole in the center of the divider for the snake to crawl through, rather than taking it out entirely) it looks like the whole thing may have some pretty decent potential as a DIY enclosure.
I wouldn't worry about the UTH/flexwatt heat on the material. You need to control it with a reliable thermostat no matter what kind of material its attached to, and that will keep it safe. If it's dangerous for the material, it's already deadly for your snake.