Even if kitty can't slice a hole...mine take running leaps and cling to whatever they grab. She could easily pull the cage over, spiling water, stressing the snake, and keeping it from reaching the UTH. If you have a lamp, that lamp is now on the floor and either reachable by the snake or burning a hole in your floor...possibly both.

The mesh won't hold any heat at all and humidifier or not, that bulb will zap humidity in the area it covers.