Event yoyos are a good thing to have, but going by sales of the previous ones that were made up, they aren't an item that's in demand. Obviously if they're included in the entry fee that's a little different, but a very small run of them would be the go.
I mean, if anyone's interested Brad still has champs Element X and Blaze yoyos for sale (collectors items yo).
As for t-shirts, I'm not really too fussed personally. I don't wear any of my yoyo shirts about the town unless there's a meet on or I'm getting paid to yo-yo so they see a lot of cupboard time.