Putting itself on the Tavern mat is a little too similar to Distant Lands, and I don't think it's the kind of card you'd want to be trashing anyway.
I think a more interesting one would be a card that can either Reserve a card from the Supply (up to a certain cost), or play a card from your Tavern mat.
Something like:
Fancy Name
$5 - Action
+1 Action
Choose one: either gain a non-Reserve Action from the Supply costing up to $4, putting it on your Tavern mat; or call a non-Reserve Action from your Tavern mat, to play it.
It has to be non-Reserve, otherwise you can gain all the Royal Carriages in one go with cost reduction.