I don't disagree, and part of my reason for giving a player bringing a concept dependent on this multiclass combination, and ideas for lore to back it up, the sideeye is exactly what you call "perceived munchkinism." I've been pretty fortunate in not having huge powergamers in the two campaigns I'm running, and I'd prefer to continue not having to deal with the phenomenon.
Well powergaming if all agree on it is also cool for a change, but not by using system loopholes. I cannot verify if a paladin / lock multiclass would be overpowered somehow, for me that MC in 5e is considered the way to power does not seem so, since all threads about it forget the costs of MAD, levels were you not shine so much, and so on and some really only watch the end result and not the way there.
Personally I shun most MC, more often than not I did not want it at my table and I think it is subpar to optimized single classes, if you got a balanced group.