I can’t speak for the devs - just my own opinion - but if you’re motivated to try then give it a go 
Just to help define further, are you perhaps thinking of something like ShinyStan and to a lesser extent Bayesplot? If so, then Arviz provides a wealth of graphical model introspection and is Bokeh friendly too. I’m not aware of anyone baking this into a GUI per se, but I’m sure it could be done.
Even further, if you’re after simple model definition like brms then you might want to check out Bambi which IMO has similar goals.
Cheers