Welcome to the RFUK forums!
I have built my own incubator but never one like you propose. So most of what I write here is guesswork. Especially as there is no mention of the species of the eggs. I have only incubated snake eggs.
I think something of the sort is possible, but I think there are some flaws in the concept. First, heat rises. So the warmer end would be at the top.
I've always incubated my snake eggs inside plastic boxes or large glass jars. Therefore, humidity in the actual incubator has never been an issue. If the incubator is ventilated and the eggs are open to the inside of the incubator, then humidity will be an issue. For example, unfinished wood will absorb humidity and dry the eggs out. And the wood will eventually start to rot.
Anyway, good luck with the project.