From what I understand, you want to be able to boot 4 isos that are on a CD and not extract the isos. uuummm... I believe, booting from ISOs is really picky. Only a select few can be booted via CDShell/BCDW (I have one iso that boots, GAG, but that's it). I would extract the ISOs you want and just use the method described in the multiboot guide. Although not completely up to date, it does work. I've never used any other boot shell so I can't say that booting from ISOs isn't possible but I do have my doubts.