Ubuntu 20.04 Power LTS: How to disable "multipathd" service at boot time, from the petitboot shell?

Question

Setup:
I have large number of multipath LUNs from SAN, connected to this system. Most of these LUNs are not formatted for the Linux env and needs to be reformatted before using.

The Problem:
To work on these newly attached LUNs, I freshly installed multipath package and rebooted the system. The boot goes on with the below error messages getting repeated infinitely. It was running the whole night when I checked in the morning. It cannot be interrupted other than hard reboot the system.

…r Multipath Device Controller.
See 'systemctl status multipathd.service' for details.
         Starting Device-Mapper Multipath Device Controller...
[ 1025.206699] blk_update_request: I/O error, dev sdkj, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[ 1025.206718] Buffer I/O error on dev sdkj, logical block 0, async page read
[ 1025.769249] blk_update_request: I/O error, dev sdms, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[ 1025.769266] Buffer I/O error on dev sdms, logical block 0, async page read
[ 1026.274594] blk_update_request: I/O error, dev sdkn, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[ 1026.274606] Buffer I/O error on dev sdkn, 

Closest matches for my search are these:

1. how-to-not-run-vsftpd-at-boot-time

2. how-can-i-make-a-modification-to-a-service-and-keep-it-persistent

3. systemd.unit

I cannot use systemctl command at petitboot to edit the services configuration as the OS filesystem(s) are mounted at different paths

Though the below devices changes during reboot, For our example, lets consider

/dev/mapper/sdc2     543137496  27507668 488017004   5% /var/petitboot/mnt/dev/sdc2 (Ubuntu)
/dev/mapper/sdd2     557858816  34048512 523243392   6% /var/petitboot/mnt/dev/sdd2 (SLES)

The only option I see to do anything to the services such as enable/disable per the description in the above links is to edit the config files at the petitboot shell after remounting the OS filesystems as rewrite. However, any edits I do to the config files from the petitboot shell is getting overwritten when I exit the shell and select/pick the respective OS image to be booted with.

Here's what I have tried:

1. Tried to edit /var/petitboot/mnt/dev/sdc2/lib/systemd/system/multipathd.service. No use
2. Tried to copy that file to /var/petitboot/mnt/dev/sdc2/etc/systemd/system/ and edit. No use.

Any file modified / created gets overwritten with the default. How to prevent the petit boot from reloading/overwriting the modified OS image after exit from the shell and OS image selected. Or otherwise, to write out the modified files to the OS images. Any help is much appreciated.