There's two very different reasons to say phrases, and your suggestions here are for something different than the circumstances you say "Good luck" in. Sort of similar to the phrase "What's up?" or "How are you doing?" - the purpose is not to respond with a detailed (or even short but accurate) explanation of how you're doing. You're supposed to say "fine, you?" You're not exchanging information, you are engaging in a short social bonding ritual in which you acknowledge each other's presence and familiarity before either moving on (either to a real conversation, small talk, getting down to some particular task, or parting ways). On special occasions, when it's the right time, you might actually inquire "Hey, how have you been doing lately? Haven't seen you a while?" and then one would respond with a serious, informative answer. Similarly, "Good luck" is not (usually) a heartfelt thing you say to earnestly convey how you wish someone to do, it's a reflexive thing you say in the midst of a complex social situation. When you do want to earnestly convey a heartfelt wellwishing, you probably want to take the time to come up with something customized to the situation rather than a short, memorizable catchphrase. The issue (as I understand it, anyway), is that one might want to build up a repertoire of short social-glue catchphrases that collectively build up certain ideas, or don't promote ideas you don't like. For example, "God Bless", even by earnest believers, is mostly an empty phrase you use as social-glue, not an earnest expression of the desire for God to bless someone, but it still over time builds up a normalcy of "God is important." I think "Good luck" is reasonable (rationalists should believe in luck), but if we do want to promoting skill, specifically, then it may be good to find something easy to say, short, which emphasizes that.