Arbo500: 1) Allow games to be marked as owned on other services. You would not need to allow people to download these games from GOG, but it should be a third ownership state (in addition to the current two: "owned on GOG" and "not owned") that affects bundles and shows up when you go to the game page. This way, if you have every game but one in a bundle, just not all on GOG, you can still complete your collection at the lowest price. While this would require the most work, it would be a great feature that I and others would use since it would save me time looking up if I already own a game on another service when a sale is on (or when trying to track down different games in the same series).
And how do you propose this feature to be implemented with the umpteen gajillion digital distribution channels out there?
Or is GOG supposed to take your word on good faith? Because I don't see that backfiring horribly at all...
2) Trust the user to denote which games in a bundle they already own on another service without making a feature for it. The method for doing this could be non-intuitive, but still possible. For example, if you add a bundle to your cart, then manually delete the games you already own, it shouldn't recalculate the price for all of them when you delete one. This would require minimal changes to GOG, and wouldn't even have to be documented well. However, it would allow GOG to continue trustings its users like it does with all DRM-free games and prevent scams.
I've read that four times now and I still don't get how that's supposed to prevent scams. If anything it invites scammers with open arms...
3) I firmly believe that the bundle price should only be slightly higher than the individual prices. For example, 80% for buying the whole bundle, 75% individually for that day, and 50% off for all other days of the summer sale. The bundle price should be better than, not equal to, the individual prices offered by other services. This still gives an incentive to buy the whole bundle, but the games aren't double the price than when bought individually. Also, there should still be a difference in price when a game is part of the daily deal, instead of being the same as every other day unless you buy the whole bundle (especially when you already own all but one of the bundle on other services). I believe this point should be implemented in addition to either (1) or (2) above, since it makes more sense regardless.
No, it makes LESS sense (apart from the first sentence which is just plain wrong).
I'll let you in on a little secret: GOG is a business, not a charity. They want to make money. And while they may not want to make money by any means necessary, they'd still rather you spend more money on their service than less. A measely 5% difference between bundle and individual purchase would incite virtually no one to buy the bundle who doesn't want all of the games anyway. Even in cases where the bundle costs less than your individual selection, while making a bit less money total, it creates revenue for publishers where there wouldn't have been one under normal circumstances. So by making you buy a whole bundle they increase sales figures for individual games, making their service more attractive for publishers.
What you're proposing would hurt their business in the long term.
I want GOG to succeed and to buy all my games from them
No, you really don't. Otherwise you wouldn't even have this problem with GOG because you wouldn't own games on other services.
What you DO want is to buy everything as cheap as possible without regard to anything else. It's all about you...