Thinking outside the box(es) requires one to identify and solve the real problem. "You've got to free your mind instead..."
All that is absolutely required is to quickly, precisely, and repeatably position a tool head and/ or sensor package within a 1" vertical envelope atop a variable x-y plane. A tender is allowed to assist with consumables, power supplies, etc. The project must be so stupid-simple that even non-technical types will be enthralled, therefore it must be designed for mass production in both traditional and Maker facilities, in order to quickly make the Open-Source and Makerspace options ubiqutous.
This implies none of the traditional linear or polar motion. By minimizing the BOM we reduce the emissions of all those ships and delivery vehicles piecing together Reprap style iterations in the hope of doing something innovative.