MBB - MBA worth it (or even worth applying to)?

Current MBB (London) second-year Analyst/Associate, beginning to think about MBA apps - would probably apply for 2024 entry with three years WE. Firm would sponsor the MBA, but I'm not sure if the value proposition is there - if I want to stay at MBB, surely I'm just sacrificing two years of tenure and income? If I want to exit (would likely focus on clean tech, either through VC/early-stage PE, PM role in Big Tech, or direct entrepreneurship myself), is it worth the inevitable debt cost and lost earnings? VC/Growth Capital/PE looks hard to do in the US so I'd probably have to return to Europe for that anyway.

Background:
Demographics: British, White, Male, Gay if it matters
Education: Oxbridge/Imperial/UCL UG + MSc (different unis), high GPA equivalents (3.8 and 3.9/4.0), technical subjects and related to field I want to go into. Already having the brand name (and networks) + MSc makes me think the value proposition is a bit less than for someone with just an undergraduate and without clean tech networks.
ECs: Strong, with some national/international press coverage, and energy/climate related.
GMAT: Haven't taken yet - cold diagnostics with little prep around 650-700. Would hope to get that to 740+ but we'll see - realise it's a big commitment to undertake and therefore wonder if I even want to begin the prep process.

Other Considerations:
Location Preference: Let's assume long-term goal is likely US based for various personal reasons, although not essential.
Burnout: Not really, have a good niche in my firm and hours are normally under 60 p/w. So less in need of a break than some MBB>MBA applicants.
US Networks: Limited, exist within my firm and a few US UG friends/contacts who have put me in touch with their own networks. 
Free to fail space: Perhaps the biggest appeal would be to try entrepreneurship and if it fails still have something to show for those two years. Seems an expensive insurance policy though. 

Targets: HSW + MIT, maybe Columbia and Berkeley.

In my case, would love to hear feedback about whether it's even worth the opportunity cost of preparing apps/attending (if applied and admitted)?