Yessss, lets do it! I'm definitely going to chuck Jim in as a rockstar (hahaha ICONS, the joy, I cannot), and totes okay with whatever you fancy with Sherlock, whether it's rival star/bandmate/journo/fan/anything at all.

And if Mycroft is a micro-managing band manager, SO MUCH THE BETTER. Jim would both be a nightmare, and be somewhat under his thumb. Ahahaha, that could only be hilarious. :D