So, I'll summarize some ideas which were generated:
1. There is probably no need to provide Wine wrappers for all games on GOG to ship them for Linux (it's a big effort). Linux users already know how to use Wine and play Windows versions of GOG games like that already.
2. If some game already has a native Linux version, why not to give an option to download it on GOG?
3. Shipping a nice distro agnostic GOG packaging for such native Linux games would be great, but will require effort from GOG (also to account for 32 bit and 64 bit Linux variants).
But why not to start with packaging provided by developers first? Humble Indie Bundle for example does that and many users are happy with it. They don't repackage shipped games, and just allow to download tarballs, self extracting archives or whatever the developers prepared. It's better than nothing at least! When GOG will have more resources and time to focus on Linux, GOG can work out some nice distro agnostic packaging as well. It's workable for multiple common distros - it's not a new issue in the Linux world. If GOG worries that without such packaging it'll look like an inferior service - no need to worry. Linux folks aren't scared of such issues and usually understand the matter. You can explicitly mark such things as "beta" service if you want. So support for such things will be limited, and you can warn about it on the download page. There can be known difficulties like configuring video and audio on Linux for certain games to work, but this has nothing to do with packaging, and GOG shouldn't be scared of these as well. Most Linux users are used to this, and will try contacting the authors of corresponding games if such issues arise. Understandably it's hard for GOG to provide support for such kind of stuff. Most recent games handle these issues quite flexibly (take for example Amnesia).
4. Even if there is no Linux version for some games, GOG can link to the WineHQ AppDB from the Game page, which often describes experiences with GOG releases under Wine. That's while not strictly necessary, can be helpful to some users who aren't yet very familiar with WineHQ. It will add to the friendliness of the site for non Windows users.
5. For games based on Dosbox and Scummvm, Linux users don't really need the Windows installer around them. So it would be nice if GOG could package such games in parts (i.e. the original game, plus a Windows installer and other stuff for those who use Windows). Splitting games in such fashion shouldn't be too hard. Linux users will download just the game, while Windows users will download both files and will have the same experience as now. (Unless some Windows user prefers to use Dosbox and Scummvm directly as well).
Related wishlist items:
* Add Linux versions of games
* Alternative OS Forum (Linux / MAC)
* Show which games use DOSBox or ScummVM