"there is some evidence to suggest that bee pollen (as opposed to plant pollen - which is the pollen before it is collected by the bees) is more nutritious."
We need to be careful with the distinction between these two things. From what I've seen where I live, and believe is probably common throughout north america, beekeepers collect pollen by using a small hive entrance holes that scrape it off the bee legs
as they enter the hive. This pollen is unprocessed by the bees. I've never seen anything but balled up "plant pollen" sold as "bee pollen" by beekeepers and health food stores, and I've never attempted to harvest anything else myself.
Once the bees get pollen into the hive, they do process and transform it for long term storage with lactic acid fermentation. We generally refer to this substance as "bee bread
". It's a much more stable product and the nutrients are possibly more bio-available for humans. I have seen references in European bee manuals on how the harvest this substance to sell as a hive product, but am not sure if it is overly common.
Comb that's had nothing but honey in it, and comb that's had brood in it are very different. You can see the contrast between the two areas on this comb
. Brood comb tends to have less and less wax the older it is and gain more propolis and bee cocoons. I'd never put larvae in a mead, my baby bees are much more valuable to me in the hive. I have melted down brood comb in water, and used that water in a mead recipes. The water and final mead were made very dark by the brood comb. It imparted a very distinct flavour. My partner thought the taste of the must was unpalatable, but I found it interesting. The taste mellowed a fair bit after fermenting and waiting a few months. At that point my partner didn't mind drinking it, and I still thought it was interesting in a reasonably good way.
I hope to try pollen as the sole nutrient in my next mead.