Never worked in a larger game-dev team before, but I always saw the benefits of Blueprints to be mainly for the ones who don't know how to code. Setup the right abstractions and you can let the level designers add interactivity for example, rather than Blueprints mainly existing for speeding up the work of C++ devs.
I think UE requires the dev team to have a clear cut between the designers and programmers. Programmers code BP "components" and give them to designers to wire them up. The heavy lifting and complicated logic should live in C++ IMO. Otherwise it's going to be hell.