[notapenny]

We used to share designers between teams at a company I worked for. It worked nicely, but the approach has its drawbacks as well, in that the person designing an extension to something might miss a lot of context that the previous person did. Especially if you constantly switch people around, you run into this.

Regardless, that doesn't address the plight of the junior. The junior shouldn't be put alone in a team and expected to effectively manage everything in that beach-ball graph, let alone be expected to come up with proper designs by themselves. That's a fault of the person putting the junior there, not a fault in the design of the whole team.