Just a point of order:
Classilla isn't slow. Not by any stretch of the imagination.
3. Speed, but considering what it's running on, Id say its pretty fast as-is and cpu tailored builds will only help to accentuate that.
CPU-tailored builds may not actually be able to do much, I'm afraid. The issue isn't with Classilla's use of the CPU, it's actually pretty performant even on a 225MHz 603, and on a 400MHz G3 it screams. The problem is that it's Mozilla. As in, the whole of the Mozilla Application Suite. And all that functionality which doesn't really get used that much takes up a lot of RAM. Let's face it, Communicator's always been a pig, Mozilla didn't fix that shortcoming at all. If there's any real speed enhancement to be made, it's making Classilla light enough that it doesn't have to page VM all the time - if it could be stripped down to the browser alone Classilla would be a damn sight faster and snappier.
And Herr Kaiser, if I manage to teach myself Classic Mac OS Programming, you bet I'll try to penetrate the mysteries of the Mozilla codebase, you may very well have a new coder. Alas, probably not soon, for I am a bear of little brain.