Good feedback. I'm new to the concept of stacking, so there's always a risk of leaving some bruised toes on the dance floor :)
This would be completely opt-in.
The guys in the mint would ask if you'd like your coins to be tracked on the blockchain; if you don't want that, you say 'No'.
If, down the track, you sell a coin to someone who does want to be the registered owner on the blockchain, he can ask the mint to assign the coin to him, bypassing you completely.
In that case, as best I can tell, the only way the tracking will have affected you is to drive up the value of your coins.
Quick Edit: It might be less confronting if we refer to them as 'claimable' rather than 'trackable'.
The owner, and only the owner, could publicly claim to own the coins.