[Darkstryder]

You do want to change the MD5 of the manifest. This is what makes it a collision attack instead of a preimage attack.

[Retr0id]

Change it to what? A specific pre-determined value? That's a preimage.

[Darkstryder]

This is indeed a preimage attack if the manifest content (besides its own self-referenced hash) is fixed. However this is not the case in practice: to pull off this trick you could just append some random bytes at the end of the manifest, disguised as ASCII art or something like that. The manifest would still be human readable and correct, but this would become a collision attack.

Again, to me this is the exact same problem as this self-referential PNG file, which is a very cool trick but which can be (demonstrably) computed with limited compute resources.