Op-amps, level shifting, etc...

[Skimask]

K, finally got some time to sit down and play with this.  I haven't whipped it up in LTSpice yet...or rather I can't   Still trying to figure out the interface, compatible components, etc.

Attached is my bodged together curve tracer schematic.  Obviously missing are the PICs doing the heavy lifting for the math, display, DAC, ADCs, power supplies, etc.
(using the circuit simulator app at http://www.falstad.com/circuit/ )

So, the question is...and I'm going to build it up anyway and see what happens...  Does this circuit look viable?
The variable resistors are going to be digital pots and one of the only remaining components to be found is the variable 'source resistance' pot, which may have to handle a bit of power.  If I can't find one that'll handle any fair amount of wattage, may have to go with relays switching resistors in/out of the line.
The ADC inputs will be connected to PICs at 3.3vdc, so can't handle negative voltage inputs (hence the diode and the upshift on the positive input of the opamps), nor can they handle more than 3.3v (hence the voltage divider in front of the opamps).
All of the opamps are going to be powered +15v/-15v...using a single TL084, which I now know won't go rail-to-rail, but I've got a handful of them to try out.  I'll switch them out later.

Good/Bad/Ugly/fair enough for a first shot at it?
You be the judge...

[Skimask]

Some days, I'm a complete idiot...
Went to start building up the curve tracer circuit for testing...using a 30VAC wall wart to regulate it down to +15VDC and -15VDC...and it's NOT a center-tapped type...
Some days, you'd think I would learn something...and remember it later on.
DOH!!!