Inline action definitions look very handy and ergonomic.
The let-power-users-do-light-dev-things is not a capability I'll be making use of (should I wind up in a position to use Avo again), though. Maybe saving particular filter configurations as a scope, but beyond that... not so much. Too much opportunity for an ill-performing query to hork system equilibrium.
I worry that you're headed down the path of recreating a crude MS Access-esque system. A product like that might be a perfectly reasonable thing to build, but it seems to me to be a different product than what Avo has been attempting to be thus far.
You might consider making it a separate product and just sharing code between the projects to get leverage... I'd imagine that orgs that want that functionality might be willing to pay more for it -- and that could help ensure you have the resources necessary to keep it from becoming a drag on development of the core system.