Yes, you can use the contents from the older games to play solo, but you will need to have trolls to fight against. Trolls are included in Gruff: Stuff of Nightmares and in Gruff: Rage of the Trolls. If you get the Combo tier, to can play every gruff and shepherd against the trolls in either Solo, or Co-op mode.
That wasn't actually a question :) I get that request a lot though. I am very interested in creating a single storage solution for all gruff contents, but to make that I need to do so at high volume to offset the cost so it is affordable for everyone. Gruff: Stuff of Nightmares is a Kickstarter exclusive game with very low print numbers. I would like to design a game in the future with the intention of accommodating a large box.
We will be having a small window after the campaign to accommodate backers in this position. The window for late backers will likely only be 2-3 weeks because we will need to lock down numbers as soon as the manufacturing order goes out.