Is a distro independent grub boot possible using a boot partition???

[Konstantin Svist]

This might not really answer your question, but there's an option you 
can use to switch from one grub to another (in stage 2).

When I was switching from FC6 to F8, I installed F8 on a separate 
partition (not wishing to destroy any of the old data). That included a 
fresh /boot partition.
Then, I added an entry to the new /boot/grub/menu.lst:

title Fedora FC6
        root (hd0,5)
        configfile /boot/grub/menu.lst

(hd0,5) was the old / partition

Since I initially installed grub to MBR, instead of partition, 
chainloader directive didn't work

HTH