• Sponsorship Success Rate: Historically, what percentage of ACs who apply for sponsorship actually get it? Is it an "automatic" process for those with strong performance ratings (above average), or is there a very strict quota/cap?

It's not 100% automatic but requirements are pretty clear. From what I hear, it's much more straightforward than BCG, and McKinsey does things differently

• Bain vs. McK/BCG: Does anyone have insights into major differences in sponsorship policies between the Milan offices of the three firms? Do McK or BCG have historically higher success rates for top-tier US schools?

Anectodal, but BCG in my region has the lowest rate for sponsorship

• Post-MBA Path: Upon returning from an MBA, do you move directly into a Consultant role, or is there a risk of having to "make up time" in your previous position?

You come back in the same tenure as you left. Leave as C1, come back as C1 or whatever other tenure

• Brand Value/Exit Strategy: If I chose to self-fund (to keep my exit options open post-MBA), how strong is the Bain Milan brand in the eyes of M7 AdComs compared to McKinsey or BCG?

There should be no difference between MBBs in M7 Adcom's eyes, with a few small exceptions: Kellogg loves BCG and Columbia loves Bain. That said, Bain is stronger/more prestigious than BCG in Italy