noturhandle from Butter here. Happy to see this being discussed.
I agree that participating tokens should be considered the extent of total voting power.
It’s safe to say that some percentage of OP tokens cannot participate in governance, e.g., exchanges and market-makers. Including these tokens in the denominator when calculating proportional governance power hides who’s in control.
Concentrating voting power in the hands of a small number of delegates absolutely threatens to entrench power, but alignment between OP holders is strong, and larger holders & delegates tend to have public reputations to uphold, so we hope 
there are sufficient disincentives for any truly selfish voting.
We’re firmly in the increase delegates camp and recently proposed a pilot to test delegate incentives at Aave.
Unfortunately, it usually requires a crisis or failure of governance for these issues to be addressed.
Would love to talk to anyone interested in DAO Governance. I’ll reach out @chaselb 