I like the idea of BPG in general, but I don’t normally associate the terms lossy with archival. Is there a particular reason to go with a lossy solution vs. (I’m assuming) the raw files?
I feel that the prices of storage drop so nicely that it would take a really large image collection to start worrying too much about it (that’s just me). I only recently switched out my primary NAS drive due to drive failure (I was miles away from filling up the 4TB).
Still, BPG does look neat (especially with animations - something neat for cinemagraphs and comparison images vs. animated gifs).