Questions for those who are against practice clubs:
1. Do you practice full swings with the same golf balls you normally use?
2. Do you honestly believe that for relatively similar flex/length/weight clubs, you swing differently?
3. Do you practice properly to begin with?
Most of you if you were being honest will say no to all three.
FWIW, I grab whatever club is handy to practice. Often lately I will use a cavity back to practice just because the range can be sandy and I don't want to scratch up my "gamer" blades.
3. No (I try ... and I probably practice closer to "properly" than most ... but yeah ... no) ;)
OK, I get that you are saying that it won't necessarily HURT you to practice with clubs that you won't be playing with, but since OP is talking about buying a whole new set, would you say that it actually HELPS to practice with clubs you won't be playing with? Or are you more just saying that it really doesn't matter?
I have a 6 iron from a set my dad started playing with in the 60's that I take to the range sometimes just for kicks. I don't think that I'm doing any harm to my swing when I break that out, but I don't think I'm helping it (anymore than I would be practicing with my actual 6 iron) either.