Hey Nick,
Thanks for the feedback!
The part about dates goes together with the Partial date entry topic. There is a workaround (auxiliary Types) that we described in option 2, but we realize it’s a 
solution. Your post motivates us to look for a better one (:
Cannot group by calculated values
Fibery grouping works (or doesn’t work) regardless if the Field is calculated by a Formula or entered manually. So relations and selects are fine, numbers and text are not.
Cannot group by lookup fields via relations
Well, Fibery does support grouping by lookup Fields. Could you please provide the setup that didn’t work for you (here on via Intercom)? We’ll take a look.