If you were to stop random people on the street and asked them what the design of a particular major brand of playing cards looks like, most would either not have a clue or a general mental image. Very few would be able to provide accurate details.
Or at least that's my speculation. I've never actually done what I just claimed as fact.
This is what I did do, however. I went with the above assumption and also considered that most laymen are used to seeing copyright and trademark information slathered over any and every thing. I came up with my own "code" that resulted in a string of numbers. As I continue to explain, you'll wonder why I didn't use letters since they would be less suspicious. And you would be right. I tried using letters but could never comfortably get over the mental hurdle of my brain wanting to make actual words out of scrambled letters line up in secession. At the very least your code will tell you the card that it is. You would need to add filler numbers/letters to it. If you are interested in a marked stacked deck then you use the filler spots as additional values. Now you would be able to know the card itself, the cards before and after it and the top and bottom cards without any calculations. With calculation you would know the exact location of any given card and/or vice versa. Once you come up with your values you simply add the copyright logo in front of it and add it to the white border. I recommend printing it in the same color as the dominant color of the back design.
An additional bonus is that it comes very close to passing the riffle test so long as your alignment is accurate from card to card.
I know that you said that you rather take away than add to so that idea may not appeal to you. Have you tried Boris Wild's system? The concept can be used on brands other than Bicycle.