[lxgr]

> How would you want to, say, transcode a collection of MP3 to Opus to fit more tracks onto the same space at acceptable quality without keeping FLACs around?

Transcoding 320kbps MP3 to some other lossy codec, once, is really not that bad. LAME at 320kbps is transparent to many people, and while I don't have any A/B test data to back this up, I'd be surprised if re-coding once to Opus at, say, 160kbps, would fare noticeably worse in A/B tests.

> OTOH, people play lossy MP3s over lossy SBC via Bluetooth and don't care

Further evidence that transcoding from one high-bitrate lossy codec to another really isn't that bad :)