Originally Posted by pollonamid
It should work with every rom that has an kexec-hardboot enabled kernel. As far as I know this is just OmniROM. You can use my OmniROM builds for SGP321. (here)
I have multirom running with cm11 as internal rom. I started with a completely wiped clean device, this is most probably not necessary but I wanted to wipe it anyway.
1. Installed cm11 latest nightly
2. Flashed Lightning Kernel: http://forum.xda-developers.com/xper...-cm11-t2882633
3. Installed TWRP 220.127.116.11: http://teamw.in/project/twrp2/185
4. Installed MultiROM
5. Ran command from Post #49 thanks to @SnZ
dd if=/dev/zero of=/dev/block/platform/msm_sdcc.1/by-name/FOTAKernel
I then installed OmniROM as a secondary multirom, but afterwards MultiROM complained and would not boot into the secondary ROM so I had to reinstall the Lightning Kernel (step 2) in order to boot from a multirom. Also I lost the MultiROM option in TWRP so I had to also run steps 3 & 4 to get that option back.
Next up was PAC ROM as a secondary multirom. Rebooted and presented with MultiROM boot menu with CM11 (Internal), Omni and PAC. Choosing PAC caused no such issues and MultiROM worked first time. Rebooted into TWRP and MultiROM functionality was still there and working fine but TWRP was now at 2.8.0 level and not 18.104.22.168 and TWRP crashed a during MultiROM work.
Again, ran steps 2, 3, 4 & 5 and all was well again so seems normal
Now I have cm11 as internal ROM, TWRP with MultiROM and Omni and PAC as secondary ROMS.
There are much easier ways you can have MultiROM as mentioned in the OP but this is one method for keeping CM11 as Primary...even if you have to rerun a few quick steps each time.