Marc Peltier has been working on a super-lightweight delta mechanic, based on the aluminum/polypropylene 'living hinge' sandwich material Hylite (his videos explain it better), and a lightweight water cooled hotend.

The speeds he's achieved for vase-style prints are simply amazing.

The mechanical-only kit is called 'Zatsit' and he's (after 3 years) launched a Kickstarter promoting it:

https://www.kickstarter.com/projects...3dprinter-with

This mechanical design brings a lot of innovative thought to the problems of 3D printer mechanics, and could be leveraged for polar and SCARA mechanics also.

Full disclosure: I'm an early funder, and have been following Marc's work for years, and wish him the best of luck!