I am in a dilemma in deciding between boutique opportunity and waiting for MBB interviews.

I have received a corporate consulting offer with ok pay, amazing work life balance and high quality colleagues (Almost all MBB) but the title is not high from Country A

I am interviewing for final round at MBB in Country B (high compensation and low tax)-they have a hard time scheduling interviews because they are very busy (even after I told them I have offers)

I am interviewing for the first round at MBB in Country C (high tax, high cost of living, core global office)

I am interviewing for a fast growing boutique within a large org in Country C (final round)

The boutique in Country C is talking about visa processing right now and ask for my info but I haven't even finished the final around with them (which is coming soon)

Living environment: C>A>B

Post Tax Salary: B>A>C

Cost of Living: C>B>A

Company brand and probably? exit oppoutnities: C(MBB)>B>A>C(boutique-niche but hot function)

I personally wont mind doing MBB at B to save some money for ~1.5 years and then move to C to live as I prefer living at C. 

Of course I can move to C and apply for MBB in Country C later but the Country C office is one of the most competitive in the world and I am not sure I can get an interview/get in and it costs at least a year.

How can I push back the boutique and make the process for MBB in Country B faster?

(edited)