Looking for documentation for Upfront

Hello - I read through a step by step guide for modifying the existing Spirit theme but I need additional documentation - for example, how to create a new, reusable layout for information pages. Does such documentation exist? Is it possible (or reasonable) to take one of the existing themes, remove all the regions and create my own custom layout/template? I don't find anything that helps define how to create a custom header or sidebar and us it on every page. Thanks!

P.S. Does WPMU plan to continue to support and develop the Upfront platform? I see very little new coming out recently and I would hate to commit to a builder only to see it discontinued.