Big tray, heated mat and leca

[IvoPhal]

I have an idea to put my recently repotted phal, Lucio and FD in a tray, at the bottom of tray made from Teflon a thin layer of Leca and a little bit of water for humidity. All this set up to be warmed at 25 -27 degrees Celsius form a heated mat?
I appreciate any comments for this cooking idea…