I seem to recall there being an X utility that detects all inputs coming from the mouse and keyboard and will spit out the appropriate name of the X server call into a terminal window. I've only used it under linux, but maybe it'd run in OS X too under X11 and at least tell us wha' t the magic switch is that happens when you place one finger on the trackpad that preps X11 for second finger scrolling. Obviously Aqua detects two fingers on the trackpad by a different method, but if we could somehow isolate what that magic switch is we could map it to a key on the mini 9's keyboard and at least get a solution that would work for apps that run in X11. And maybe it might give a hint for how to intercept that input for Aqua as well.
In an ideal world (without hardware hacks) the best solution would be to map one of the mini's keys to the magic switch so that the use presses down that key, which turns the trackpad into a giant scroll wheel until the user lifts the key.
I'm thinking out loud here, so ignore the above if it doesn't contribute anything. Just a brain dump