I have been rad with the Nexus5 where rootfs is not constrained by a small physical partition size. I wish all devices could be converted to that layout.
So far I enabled very easy resizing of rootfs via atuTools4UT: https://sourceforge.net/projects/all-things-ubuntu-library/files/releases/

And the related portion in the sourcecode: https://sourceforge.net/p/all-things-ubuntu-library/code/HEAD/tree/trunk/ATUpackages/ATU/ATU-src/atulib.pas#l1329

Currently working on a GUI for also resizing rootfs based on physical partition layout, ie. on Meizu PRO 5. Not sure if I will be able to do it on-device, but am still exploring this possibility, even using pivot chroot method.