Tyler,
It seems you are using the standard "because racecar" approach to solving your problem. Namely, chase the most complicated and expensive solution you can find. (And if you think spending yet another ~$600, AND making a new diff-case, is NOT expensive, then please send the money to me!
)
As noted by others above, there are many simpler and cheaper fixes to your problem. Please re-read CWA's posts, and also get your suspension guys to read them several times. There are many clues there that can help your Team build a faster car.
Regarding your list of options/goals for selecting a diff, I think you are somewhat missing the point. It is important to realise that you need the "whole package" (= diff + suspension + everything-else) to work well, and that means you cannot just choose a diff based on a simplified list of "diff characteristics" taken in isolation.
Because cost is so important (to me!) I would immediately narrow my diff choice down to these two cheapest options.
1. A "spool" diff.
This is about the simplest machined part you can make for the car (= lathe + drill-press?). (Or you can turn your current Torsen into a spool by squeezing some extra washers in there, or filling with epoxy, or weld...) Your current car seems to be already "set-up" for a spool, so no extra work there. And, most importantly, there are countless cars, both past and present, that have won FSAE comps with a spool. The "spool causes understeer" is one of those lame arguments that might be true of a spool in general, but has turned out to be irrelevant with the car set-up used on many winning FSAE cars.
2. An "open" diff.
Your Torsen is close to this, though cheaper ones are available from any car wrecking yard. The set-up changes required on your car, to suit a fully open-diff, are quite easy. From reading your above posts I suspect your suspension guys are, ... ummm, a little lost. [Well done Z! The politeness lessons are working.] Short list: Fit stiffer front springs, and/or softer rears. Or a VERY stiff front-ARB. Make sure frame is torsionally stiff enough for this to work!!! Make sure front dampers reach droop limit before rears. Reduce excessive "steer-wedging" from steering geometry. Beware of VERY short end-view Rear-Virtual-Swing-Arm-Lengths. And some others ... but the above should cover it. Personally, this is my preference because I like the idea of having all four wheels always planted.
The choice is yours, of course, but throwing money around does not equal good engineering. Besides, I am sure you will eventually meet a girl who will teach you how to really squander your hard-earned dollars!
Z
(PS. "A good engineer is someone who can do with one dollar, what any fool can do with ten!")