Why first-rate ships served as fleet flagships

If Britain built first-rate ships as large as the French examples, would they serve as fleet flagships?

Yes. Royal Navy first rates already filled that role, although Britain generally avoided the largest Spanish scale because it made ships difficult to handle.

Large first rates already served as Royal Navy fleet flagships, so the proposed role was historical rather than hypothetical. Britain built substantial ships of the line but did not chase the greatest Spanish dimensions. The panel's objection to the largest examples is practical: extreme size could create an unwieldy ship to navigate. The exchange ties flagship prestige to the handling tradeoffs of building ever larger sailing warships.