I don't understand my proposal as related to signaling at all

What's the good reason to care about whether EY's salary is calibrated to the market rate, rather than/independent from whether it's too low or high for this particular situation?

it's about measuring EY's (and others') effectiveness, rather than taking it for granted.

I don't understand why SI (i.e., its board) shouldn't employ EY and MV full-time and continually evaluate the effectiveness of their work for it, like any other organization in the world would do.