I have finally finished this COVID-boredom build. Went quite a bit overboard, and also went deep on the Alibaba/carbon knockoff game. I'm not sure I'd advise a fully grown adult to ride this stuff, but for a 40 pound kid I think it is amazing for the value/weight ratio. In fact, most of the stuff seems better built than a bunch of Easton EC90 stuff I paid ridiculous amounts of money for back in the early 00's (and that was at pro-deal prices!). Anyways, attached is the complete build list (new parts in bold), and a couple pictures:
Attachment 418022Attachment 418023Attachment 418024Attachment 418025Attachment 418026
Very happy with the way it turned out, and lost around 7 pounds from stock (!!). It is now just a hair under 18 pounds, which for a 40 pound kid makes a world of difference from stock. Also extended gearing and losing the boat-anchor suspension fork (that she could not even compress at lightest preload settings) make for an actual trail rideable 20" bike. She loves it...