Keeping in mind that I know VERY little about burms, I have a suggestion to put in for your consideration. I don't know how much a burm is going to climb and use the vertical space of the cage. (Correct me if I am wrong here) If that is the case, why not install a single sheet of plexigless across the top 1-2 feet of the cage? Said plexiglass could act as a divider, allowing you to put frogs or geckos or something that doesn't require addition heat into the vertical space, without the sanitary/safety issues which everyone else has already brought up. If would essentially be like having two enclosures in that space, and you could remove the plexiglass later when the burm outgrows the enclosure and you get something else.

It may be a horrible idea, other people will have to comment. Just something to consider before throwing some poor little froggies in with a burm.