I just sowed "aphrodite mix" alyssum seed... if I get good germination, I'm hoping to add a couple 6-packs to my swap list. Hopefully I can trade you some mix for some purple, if you want. I lost my "crop" of them last year so am not listing them just yet!
You're right about not being able to reserve plants for people... but if those who have asked will sign up for the swap (on the "Seed Swaps tool"), they can add parsley to their wish list and be ready to click when trading opens.