Small RX Firm --> Big 3 RX Shop --> Buy-Side?

I am working in the treasury department at a very large private company and am currently interviewing for a small boutique RX firm (it's one person at the moment). The firm has a middle-market focus and works in several industries, with both creditor and debtor work. 

How doable would it be to transfer over to a Big 3 or "elite" RX boutique firm after working there for a couple years? It seems like all job postings for A&M, Alix, and FTI require some sort of restructuring experience, so this seems like a viable way to break into the industry. Would I need to get my MBA in order to break into a Big 3 RX firm given the small boutique RX firm experience?

Additionally, what kind of risks do I run working for a solo RX shop? I believe the firm is expanding, so that is definitely a positive. End goal after getting into a Big 3 would be to either stay and advance, or explore buy-side related roles.

Any insight would be appreciated.

Thanks