Exactly. Other self-funded classic RPG project - Age of Decadence - used this approach, sharing its working beta with backers as it expanded. At the current stage the AoD backer beta includes about 2/3 of the game's content, AFAIK, and it's pretty awesome. The game is available for pre-purchase on steam, and a big working beta is a great incentive to buy into the project well before release. (although the game itself is only for hardcore CRPG players, it's pretty unforgiving).
Yes, but AoD has been in beta for like 4 years.