Would treated CD's or OOP's-hold its value later?

Yes, just like circumcision, there is no going back. The good part is that it hurts quite a bit less.

All kidding aside, pretty much any modification of a CD would diminish the saleability of that item in the market place. Does that mean that you can expect to get less money for it? Probably, but not necessarily. It will certainly limit the pool of buyers, as many collectors will not touch an altered item. But it is possible that there are buyers out there that would still pay you $100.00, though I would not give you more than $10.00 for it. And the more rare an item is, the less likelyhood that they will have a choice between an unaltered example and your modified example. In the end, supply and demand are king, but remember, you only need one buyer. Those are the vagaries of a free market.