When Loadlin isn't available, you to have to resort to something else.
Boot Linux copy your kernel directly to a floppy. However, if it fits, I'd make a LILO based floppy so you can pass parameters to the kernel. This is your backup copy and you can rip out as many as you need; hopefully you won't need it.
If you have concerns about your MBR, you can always put the boot information on another partition. I tend to cheat and create a small FAT partition and use that space for handling booting.
BootMagic by PowerQuest (this comes bundled with PartitionMagic) is an excellent way to get things to a multi-boot state.
When using the BootMagic solution, it takes the MBR and runs the software from any FAT-based partition. BootMagic does some clever things like hiding and unhiding partitions selectively befor starting the OS. This gives you the ability to make each OS think its sandboxed on the disk.
I think you'll find BootMagic the easiest (and affordable) way to go.
Since you already have the OS's installed, BootMagic should pick this up and do all the "hard work" for you. So it sounds like you just need a good boot commercial manager if you aren't up for LILO.
Best of luck!
