Option 3

My reasons:

1. As others have stated the DBI framework doesn't promise the example you outline to work so you aren't breaking anything that isn't already questionable, if you can even consider that breaking.
2. I don't advocate that syntax for a way of getting a count result. It to me is one of those "you could do that, but why?" kinda of things.

As long as you document the change in behavior I think this is the best move at present since you seem to be solving a larger problem then the one you may have created with the changes.