I would like to propose a no builds variant - stalemate lines are almost impossible to form without building, destroying units become paramount for defeating your opponent (but also much more difficult) and well the other awesome thing about the pacifist variant is impossible without making rules for voting on a nomic game.

But let's try, the 'UN' gives out 1 vote per SC.
You can call as many votes per year as you like.
Votes can changes the given rules.

rule 1: no builds.
rule 2: each players gets 1 vote per SC.
rule 3: votes require a majority(half plus 1) or at least 18 votes.
rule 4: all votes are public.

I think it is implied that you can try to influence the way someone votes by offering something like supply centres.

It is also (implicitly) possible to call for a vote that you win, though until you get to 18 centres it is impossible to guarantee such a win (at least with the initial rules)