I would love to see a thread on this! Watched a few みんなのうた on random when Malaysia used to have NHK World Premium channel by an IPTV provider I’m using. There were a couple of songs that strikes a chord with me musically (due to how old school, out of the world and weird it sounded) and tried to Shazam but couldn’t find any links.
So maybe with your compilation, I might just find it again within the list. But even if not, your extensive list will still be a pleasure to watch and listen while learning Japanese.
Thank you so much for doing this! 
P/S: I think in the particular one I was searching for has a kid playing trumpet or an instrument out of tune, yet it “matches” the overall upbeat sound. That was one of the hilarious ones I’ve heard! Last but not least, the original “Oyoyo Man”! I could only find the spoofs or covers on Youtube, but not the one I saw on NHK >.<