Either way, it's still going to be ever so relevant on RoatPkz. The sets will NOT be expensive, Dharok's and Ahrim's would most likely be 300-400 pkp a set, which is not that much (my opinion on what the price should be). It's 3-4 days of voting for 100 pkp, plus they can pk in Rune/Dragon armour on here. Rune isn't as weak as you would think. Anyway, Dharok's isn't only not liked by bridders (which doesn't make up as much as the server as the forums would make it seem) but also by a lot of pkers because of how fucked up it is. You hit what you should at low hp when you've got high hp, and vice versa. If it gets put into the shop, it would still need to be altered/fixed because it would still have the same problem. Putting a price on it helps, but not as much as it being more like what it should be.
Player growth would not be halted or even affected if this change were to happen. People would stick around because it is so easy to get PKP on here (was for me anyway).
I don't think all the barrows armours should be added, leave out Karil's and Torag's. Verac's and Guthan's are both underrated and underused imo.