Wouldn't that make later pokecentres more expensive seeing as they have more expensive balls?
I'm not sure how that'll work out but let me know how it goes.
I think the main challenge in nuzlockes comes from preventing overlevelling or soloing, so any ruleset that achieves that is good in my book.
I can say from experience that my customised nuzlocke is definitely a challenge. I blacked out with no pokemon in the PC at Misty in RBY, and I understand RBY at a competitive level.