[Sprint  Galaxy Note 4 General] samep:
I don't know if anyone has tested Beastmode 1.5 kernel with systemless root? I haven't. But IMO, Beastmode is better than stock.

At least with stock kernel, root relies on patching with systemless SuperSU. For systemless root to get established with a backup that reboots after loss of root, SuperSU systemless script backs up the stock kernel and also makes an su image during the script. I think your steps are missing the correct order: stock system restore or Odin stock tar, run systemless SuperSU script on stock kernel. You can use either CFAR or Odin TWRP and recovery flash SuperSU 2.65 beta.

To establish systemless root, the older system-based root must be removed. Chainfire recommends flashing stock system and restoring stock kernel first. I recommend Odin stock tar for that if your backup is suspect. Perhaps it contains the older freeza kernel that required patching but the security update was breaking that one?

Problems I see with systemless root may prove too unstable for some users or custom kernels. Some apps may cause root loss when ran on systemless root. Systemless root backup and su image allows root restore on subsequent reboot without looping but that may not happen in custom kernels because the systemless patch script may be exiting before the backup and su image get set in place for this happen? I saw this happening with freeza's earlier kernel and systemless SuperSU 2.60 and possibly through 2.65 but not positive on that but I think the main issue was the security update making patch unstable.

In your case for sure, I'd recommend establishing systemless root with stock kernel before trying to do that with Beastmode unless there's a confirmation with step guide posted at some point.

So the systemless root guide with stock kernel is simple:

1 backup internal memory to extSdCard

2 power down

3 Odin stock tar, auto reboot to establish data sync and GPS lock.

4 Odin CFAR

5 Busybox from Google Play or install TWRP with Flashify and flash osmOsis busybox in recovery. The more you do, the more you risk breaking systemless root. I do believe titanium backup has been demonstrated to need busybox to work properly. Correct?

Just how stock are you trying to retain? You may need TWRP if going to flash a sound mod. Those heavily modify system. I was losing systemless root with that and apps I run but reboot would restore root with the backups. Systemless root may work best if system is untouched. Some apps will require busybox; if so, use systemless busybox.

I think the process would be slightly different on Beastmode 1.5 with systemless root (untested? needs confirmation)--(edit: I believe I got confirmation today- it works but untested for reliability)

1. Repeat steps 1-3 above.

4 Odin TWRP (rather than CFAR)

5 Flash kernel in recovery

6 Flash SuperSU 2.65 beta

7 Flash systemless busybox by osmOsis

http://xdaforums.com/showpost.php?p=40409356&postcount=1 scroll until link for busybox is found. Actually the script will install either the systemless busybox or system based busybox automatically. Works with any and all SuperSU root methods.

I've been using another script by osmOsis, unSU, but some reports I'm getting is that it doesn't work as well as restoring system and stock kernel prior to flashing systemless root as Chainfire recommends. You could try that rather Odin or flashing the ROM again.