I assume using them for a game is redistribution? It's just that some parts fit and some don't, often... and many are medleys, which means the tone changes, and often a narrative doesn't change as quickly. Also, music in games tends to repeat and not have fadeout endings.
You can do that for yourself, for your personal collection - absolutely, no one's stopping you, and why would they...
The key word here is "redistributed" - if you're hosting/mirroring portions of the collection for *others*, yeah, we want the files to be official & unmodified. If you're remixing them, that's no longer redistribution of the original audio, it's a different ballgame entirely. Conversion to OGG wouldn't make much sense (lossy to lossy?) - @Liontamerhas done work on silence trimming so if you find mixes w/ 10+ seconds of true silence (no signal), let us know here. The bigger no-no that we're especially concerned with would be modifying tagging/attribution, FYI.
"If OverClocked ReMixes are being redistributed, they may not be modified in any way from the MP3 versions"
...I mean, really? Remixes can't be remixed? MP3s can't become OGGs? That 10 seconds of silence at the end absolutely needs to be retained and thus ruining what is otherwise interesting music?