Why not make it a trait that while you get, there's a UP vote where the other races get to say (obviously you can vote for the largest number if you've got enough diplomatic grunt) how many turns free from Drengin/other race harm you get. This ties it in more to your choices based on the Galactic Events and your relations with various players. Why should the Drengin, who hate you because you culture flipped Kora IV, wait for 100 turns before bitchslapping you?
1: The trait can stay as early in the game as it currently is, tier 1
2: What you get is like a voucher, it's up to the UP vote what numbers written in the xx of "This Voucher Entitles The Bearer To xx Turns Of No Attack".
3: Occurs to me as I'm typing this that if the UP votes and you end up with 1 Turn Of No Attack, even as an easy Teir 1 trai to get you'll be wondering why the fuck you bothered?!? Queue rage quit. Once you have that trait which obviously is yours for life, you can - one you're diplomatically cool enough or can force it via economic/cultural power - periodically front the UP and ask that you get a vote on how many Turns War Free you're getting this year. Note: This vote by it's nature will make your diplomatic relations with every race take a hit, you are rubbing noses in dirt and you can only do it when your relations with the majority of UP races are good - ie 6 other races in the UP, you have to be on good relations with 4 of them.
4: This is true for all races (to stop the player from becoming too powerful), ie the Drengin have the same trait and want to force a UP vote because of my "Matey With The Majority" rule. This provides scope for major dipolomacy between the races before the vote with regards to who'll vote for what and what they'll get for that vote.
Should this trait be tradeable - either permanently or as a loan ie Drengin will get Neutrality from you for 500bc but must give it back in Turn 50. you restrict them by limiting the time they hold your Neutrality Voucher and therefore what they'll get from going to a UP vote for the Turns of No Attack number? And, once espionage is up and running, stealable.
And of course if you're the aggressor the Voucher becomes void.