I definitely support the idea of making some changes for classics to have more of a incentive to do some PVP. The only thing is how to make sure it would be balanced and not something that could be taken advantage of like other people have stated with PKing farming void sets for untradeable cash.
A quick suggestion I could think of could be the cash/items whatever it would be will be based on what the other player is risking for example the bounty hunter skull in the wild shown below
So basically on what tier it is would be decide how much the classic PKing gets, both classic and other player has to be skulled. I don't see how this would be an advantage for classic mode as the items a classic pker gets off a normal acc gets wiped out the game for a 200k-1m cash drop.
This was just something I quickly thought up maybe someone would be able to expand on it or get another idea that could work but I do believe a change in PVP for classics would be great.