You might be interested by the board I've designed. Not "RF Nano" but "RF Pro Mini". Of course you need a "USB to serial" programmer but it directly runs on batteries.
See here and here.

thank you! this is a really good question. I now understand why you didn't incorporate the radio module. Is it the only reason? Have you investigated ways to certify a product? It is a pity if you can't incorporate the radio but we need to add extra modules that are probably not certified either. I am not willing to become a vendor (just providing a design and a few units). In that case, I don't think I need to make any measurements. Of course if one wants to go further in the industrialization process, it is a mandatory step.