I agree.
This is a huge issue for most powers.
I have proposed this solution before:
Make voting count.
In the current iteration of gameplay mechanics the voting rights people earn are virtually meaningless, and might as well be removed.
Instead, make them really count. For instance, let the voters decide on which system from the preparation list to expand into. Let voters veto undesirable systems for expansion. In short, remove merit count as a deciding factor other than getting systems on the list and let the votes decide. This would add truly strategic decicion making, as well as take power away from merit grinders or fifth coloumnists.
Further in development, the ability to vote on alliances or declarations of war could be added in.
Cheers.