Thanks for your proposal!
I agree with the reasoning and think it would be a good idea to increase the threshold. Historically, since PIP-33, most of the proposals got at least 200% of the quorum (29 of 31).
However, I’m not sure about the new threshold suggested. (22 of 31 are above 400%). This could introduce unnecessary difficulties in the governance process, and the impact of the DIP is not well-known yet.
27 of 31 proposals got over 300% of the current quorum (I believe it translates to 6% of the circulating supply). It seems a well-balanced choice between enhancing the governance resilience and introducing requisites that may hinder the process.
I hope it makes sense!