Back in the good days, we simply had these things called expansion packs. They did exactly what was described here, until they were replaced with money-grubbing DLC.
@Rat_King A quote from the FAQ on Obsidian's website:
"Once the Kickstarter ends, every backer will receive a survey asking them what platform and distribution network they would like. We now proudly support both GOG and Steam, so if you prefer DRM-free, you can choose the GOG option, and if you like Steam's integration, including achievements, and possibly cloud saves, you'll be able to choose that as well."
Sanligo's comments