Being able to define taps based on the current location would certainly be useful, and I've often desired it when building games myself. However, right now, it's not possible. We'd love to put it into a future release, but it won't be soon -- even figuring out just what the xml for it would look like isn't obvious, and the underlying engine changes would be even bigger.
This wouldn't work for all cases, but one alternate option may be to essentially put actions onto the location itself. This isn't possible right now (though would be a smaller change to add in the future), but can be easily faked. If you create a location on top of your existing one that takes a difference piece_type, you can add a piece that has a transparent image, and isn't draggable. This can have actions assigned to it for taps, that will take precedence over the pieces below it. However, it won't interfere with piece movement or display.
For an example of this, you could look at the block stacks in Castle Capers. The game file is pretty large, but it includes just about every feature in EveryGame.