Yup, that would work. Although, I think it's over-engineered and fragile compared to changing a single line of PHP (which is what each of the proposed patches do, excluding style C).

I think client-side vs. server-side is a false equivalence in this case. Firstly, coming up with a perfectly reliable client-side OP caching/lookup scheme is a much bigger engineering effort (which should be taken as a sign, IMO, that the work is being done in the wrong place).

Secondly, a server-side implementation automatically benefits every forum member, instead of only the members that are willing to install browser extensions.

No problem, I'm happy that it won't (seriously) disrupt any of your data wrangling!