So I made an installer than includes all of these and has no extra dependencies needed. Just install and go. The only thing it doesn't currently have is support for syntax highlighting (needs PyGtkSourceView, which is not included in Portable Python, which I used), and VCS browsing (needs GNU Patch via Cygwin). Here's where you can get it: http://code.google.com/p/meld-installer/. Lemme know if you find any mistakes, it's my first time using NSIS.
Edit: I've now also created a portable .zip archive.
Edit: I've made a significant update to this. My thanks to Angel Ezquerra of TortoiseHG for his suggestions and testing assistance.