Hi @DavidD Thank you so much for taking the time to share all of this! 
I shared your toggle use case for single & bulk selection with our team -- makes sense!
I have a couple of follow up notes for you--
I have never utilized the filter functions in the legacy table and have always opted for custom building my filters with other components and not foreseeing moving away from that (and would put that at the bottom of my priority list)
Noted! We found that was true of a lot of Retool builders when we did our table research. I believe we're actually working on a separate filter component, which might end up being interesting for your apps 
Something major that seems missing (and perhaps I'm just blind) is the custom button being available in the toolbar as well as the download as CSV option.
Yes, this has been one of the top requests for the table & we're currently working on adding this!
changesetObject
This is helpful feedback! Would something like this be helpful for the time being? 
I've also relayed your actions feedback internally! Thank you