I hope that some swaps get started specifically FOR rare and precious seeds. Those swaps can test and refine mechanisms for fairness, freshness and pollen parentage.
Maybe they would even support negotiated one-on-one trades and three-way trades, or "I will make THIS available to whomever, but only if I get one of the following from someone ..."
I assume there will also be "mass market" swaps with relaxed rules and high volume, and maybe a phase for older and re-traded seeds.
Then people can join the swaps that lean toward their preferred style of trading.