Do a search of the forum for multiboot ..... there are a few threads on the subject and also a few methods that can be used.
In general the PCLOS ISO cannot be booted of itself using Grub Legacy ... files need to be extracted from it and then they can be booted.
In your situation it seems the simplest thing to do would be to install Grub to the boot sector of a partition which holds the OS files to boot, and you can then chainload that Grub from where ever you wish.
Having a live PCLOS on a partition for emergency/recovery is sometimes referred to as a 'poormans' install, so that might also throw up some threads.
I have used various OSs on a live USB drive along with a few PCLOS versions.
The same can be done on a partition of a HDD without much problem.
I have one such on this PC, but have not had to use it thankfully.
I only used Grub Legacy without any other boot manager, so have no info on what the requirements of any other boot manager would be.
So yes, it is not difficult to have many different live OSs on a partition of a HDD for recovery.
The details of how to accomplish it will depend on the boot managers used.