I’m happy to take suggestions for a future campaign, but for this campaign, I’ll be sticking with sets that are ready to go! That way everyone gets their tiles nice and quickly. Tiles sets are super time consuming to make, and who wants delays? NO ONE THAT'S WHO
I do not offer that as a feature. Some brands, in some colours seem to work ok, but others stains the tiles, so it’s not a feature that I claim for these tiles. Please be very careful marking your tiles with any kind of pen - I do not recommend you do it.
I found some good two-part plastic boxes in Hobbycraft (in the UK) which provide a good selection of fits. I have also used pockets in a lever arch binder to store each tile separately, in order, so I can lay them out in the order I want.