StingingVelvet: Quake 64 is just an interesting port rather than a completely different game like Doom 64 is, apparently, so I don't think it would be a huge loss. That said I do of course hope it is included (and made DRM free on Steam as well).
Uhhh, it kinda is DRM-free on Steam already.
Here's the thing: Once you sell your soul to Satan (by setting up a bethesda.net account), you can access the add ons and download Quake64. Even after you download the Q64 files, you'll have to go through the (bethesda.net-tied) add on-button in the main menu every single time you want to play Q64 - however, there is a workaround.
- Start Q64.
- Save your game
Congratulations, you now have a DRM-free backup of Q64! You don't need internet access, you don't need to activate Q64 via the add ons menu, you don't even need a bethesda.net account to play. All you need is to reload that savegame you've made while playing Q64.
Add ons being tied to bethesda.net is completely arbitrary bullshit, probably an effort to get more fools to sign up for their shitty service (hey, worked for me!). But no, you wouldn't actually need this crap to play the add ons, once activated all the required files are stored on your PC and every time the game has you sign in to bethesda.net they're making you jump through artificial hoops. Best solution for gog customers would be to include Q64 by default (it takes up about 90MB, the resulting bloat should hardly bother anyone).