This is a kind of general problem of voting systems when several opions are eligible. In your example with starbase modules, where there are 4 options, sometimes the vote can be decided by as little as 25% + 1 votes, when all other players spread their votes on the remaining options individually.

The most democratic way (means: the majority of votes rules) of doing it would be to eliminate the least wanted option one after one by majority in successive voting turns. If there are x options to choose from, this would require x-1 voting turns.

This procedure isn't practical in many instances. One can make a trade-off, e.g. the French presidential elections, where the first voting turn eliminates all candidates except the two "finalists" for the second turn, from whom the president is finally elected.

I find the current system perfectly adequate, because it is simple.

It would be nice to see what the UP vote would be before actually going into it. Sometimes in my bigger game, I lose track with what may be going on, paticularly with how some options may in fact benefit one AI or another. It would be nice also if there was a limited diplo option so that the player can ask others to vote for one paticular option or another. Of course, I'm only playing DA at the moment, so I'm not sure what has been changed with the latest expansion.