Well I don't think there's one easy tool to do this, but I have a bunch of suggestions on where to start regarding Logic's panning. First off, you should skip the pan knob in the mixer window, and use the Direction Mixer plug-in instead. Here's why:
http://nk-e.com/2010/01/30/panning-the-logic-pan-as-in-dont-use-it/
So now regarding your placement questions: You could probably answer this 100 different ways, so here are some questions:
1. How detailed to you want to get?
a. you could compress, eq, and use Stereo Spread on each individual track. this might take a while, but might give you more control.
b. you could create any number of aux tracks, where each aux track was a separate frequency/imaging setting. that way you could just adjust any individual track's send knob to go to that freq/space combo.
2. What kind of music are you doing?
a. does your style of music require certain instrumentation? for example, if you're doing Celtic music then I would treat the mix a bit differently than if I was doing an Icelandic techno song.
b. do you (or your intended fans) care if you mangle the sounds?
Also, have a look at the MultiMeter plug-in. Speaking of plugs, you should definitely check out an Audio Unit called "Stereo Tool" from the fine folks at Flux (say that 3x fast):
http://www.fluxhome.com/products/ Nowadays there are so many ways to do things...maybe someone else has better suggestions? In any case I hope this helps, lemme know how it works out.
sb
