Truth be told, i'm not a fan of card ideas that change the effect of other cards while they are in play. First, they create rules, which are not necessarily impossible to overcome, but can become confusing nonetheless. All "if you would" is complicated - consider Donald's remarks about Trader. Also, they do not stack usually. Most of the time i think sticking the ability on the card directly is the better option. An example would be Co0kieL0rd's Beachcomb, which reads:
+1 Card
+1 Action
Look through your discard pile and put a card from it in your hand.
Obviously this is not too rarely better than Lab, although it gets weaker when your discard pile is empty. Note how it is never entirely useless and never harms you. Unwittingly harming myself isn't something i like to do. I'm not saying this is perfectly balanced (his card costs $6 and has a Reaction to avoid strictly-better discussions), but it's the better implementation in my opinion.