I've been in private conversation with Shahrokh about fixing some bugs in expr and improving it a bit. See if he has anything to contribute now in the very short term.
Now for my so called "objection". Well, I just have an issue that I'd like to bring to your attention :) which is this fix for [sigmund~] -->
https://github.com/pure-data/pure-data/pull/2445 and it's actually something we also have to fix in the documentation, and that I don't really understand how it works. I think it'd be good to also take care of this for 0.55-2