Modder’s pack. In addition to a beta and release (and, I guess, digital pet dudes), access to modding tools as early as possible. Includes prepackaged versions of any free tools, or barring that, links to download sites and all their dependencies - just make getting a modding setup as painless as possible. If you can include some kind of instruction booklet/tutorial pdf on using the tools, all the better.
The sticking point, I’m guessing, would be Qubicle. However… it might be possible for you to work out some mutual-promotion dealy with them where licenses go at a somewhat cut rate when packaged with copies of your game. Let’s be honest, you are sending a certain amount of business their way, and the fever of of a Kickstarter campaign could work very much to their benefit.
As long as the total price of packaged software plus games does not dip below the price of the software alone, there isn’t a significant incentive for Qubicle’s other potential customers to grab the package. However, Stonehearth players do get an incentive to go into the modding scene, and Qubicle sales should have a net uptick. Looks to me like everyone wins.