The Harmony will hardly work. My solution was to buy an IR redirector. This way you have a tiny IR receiver outside the cupboard and the small transmitters are distributed around the cupboard in front of the devices you want to control. This is how it works for me with 2 transmitters and 6 devices and 1 Harmony.

Digitec has various IR forwarders on offer. Here is an example: One for All Ir Remote Extender Global

I think it depends a lot on what the cupboard door is made of. The remote controls work on the IR principle. This means that a wooden cupboard door blocks the radiation. A glass door should work. I don't know if there are problems with tinted glass.