Not much else to say except I made images of TWRP 3.0 for the Nexus 6 that have F2FS and MuliROM support.
All credit goes to TeamWin and the MultiROM team for their work. I just added F2FS support and made images.
Download: TWRP 3.0. with F2FS Support
Download: TWRP with MultiROM and F2FS Support