Being at work, I don't have access to my copy of Race Car Vehicle Dynamics, and I'm not 100% sure this would be in there anyway.
Is there a way to calculate "ideal" spring rates? I.e., using a vehicles corner-weights, roll-centers, spring-rate to wheel-rate ratio, &c, &c, can one determine an "ideal" rate, or at least an ideal range of rates?
Just spitballing it, I'm assuming that a minimum spring rate could be determined using the spring-rate to wheel-rate ratio, gross weight, and fore/aft weight balance. i.e., for a 3000 lb car with 50/50 weight balance and 1:1 wheel-rate:spring-rate, I'd assume that the springs would need to be able to support 750 lbs each, and assuming a 3" travel with linear springs, that would make for 250 lb/in springs on each corner.
I'm assuming that a "maximum" spring rate would be assuming that each spring would be suspending 50% of the vehicle's weight, rather than just 25%, so that would make for 500 lb/in springs.
I could keep rambling along these lines, but I have the feeling that would be trading my shovel for a backhoe when I'm not even sure I'm digging in the right yard.
Am I anywhere in the ballpark?
I think you're in the right ballpark, but my binder from OptimumG is at my shop so I can't check. I'm pretty sure it's got some stuff along those lines.
The only thing I thought of when I looked through your idea is that when you assumed 3" of linear travel to support 750 lbs/corner, thus 250lb/in springs, that would give you 3" of droop from ride height.
Under cornering, the forces on each corner change dramatically (duh) and you have to factor in those changes. The way that's coming into my head to do it is to determine the maximum cornering load you're going to be working with (seldom much over 1G on a street car like I assume we're talking about), calculate your motion ratios and vertical center of gravity to figure out how much compressive force 1.2G of lateral cornering load would result in along that specific corner, decide how much wheel travel your chassis would be able to handle, and find a spring rate that fits somewhere in there.
I know there's more to it than that, but I think for our purposes it's easier to look at what other people are doing and just guess.
I agree 250 lb/in would be too soft for performance in the example above, that was more "how much spring do we need just to hold the vehicle up".
I'm honestly not sure how to translate the lateral cornering load into vertical spring load, which is why the second part of that example I just assumed that the outside wheels would be supporting 100% of the vehicle's weight instead of the resting 50%, however, the more I think about it, the more I'm thinking that load could exceed that, especially in cases of > 1.0g.
Not having a physics requirement for my degree is starting to haunt me, I guess, hahaha.
Some people will use the spring frequency to calculate the desired rate. You'll need corner weights, the motion ratio of the suspension and the unsprung weight to figure it out.
http://autospeed.com/cms/title_Springs-and-Natural-Frequencies/A_108167/article.html
Lateral cornering - calculate your weight transfer and that will give you the vertical load on the springs.
Inertia force = (weight x acceleration)/g
Weight transfer = (inertia force x cg height)/track
Thanks for that article, Keith. 
What this is all working towards knowing WHY the right rates are the right ones when I do the Cobra suspension this winter. I'm looking to convert to a torque arm in the rear and coil-overs up front, so no easy "buy aftermarket spring kit X" for me.
