I'm certainly no expert, but il chip in my 2c.
if its a track based car, i'm tipping your on semi's?
anyhow, 2.5 -ve degrees up front maybe isnt enough, I run atleast 3, mostly 3.5 and mine see's the road once a fortnight atleast. (not many kays tho)
on the rear, 2.5 -ve sounds to be too much, i only run 1.5 -ve on the rear.
you dont mention ride hights, but the "recomended" ride hight for gtst's is 350mm front, 340mm rear, thats from guard/top of wheel arch to centre of the hub.
nolethane bushes are a good idea for the rear LCA's.
adjustable front and rear UCA's is a good idea (rear traction rods also), and front LCA's are handy also.
what type of diff? stock? shimmed? or 1.5/2 way?
as for steering maybe 'new' tie rods & rose jointed tie rod ends?
and for track work, depending how serious you are, most people would recomend ditching the ISC coilovers. I'm in the process of ditching my teins for bilstein shocks (with extra hight adjustment grooves) and king springs (6.5ish Kg & 4.5ish Kg).
0.5 toe out up front sounds okay, what you running on the rear?
hope this helps, Jack