My view of modernising the MKIV Supra is quite simple :
INTERIOR :
FACELIFT,
Full interior LED (with new not yellowed buttons),
Leather RECARO,
Leather facelift 3 spoke stearingwheel (out of the IS300),
Leather rear seats,
EXTERIOR :
FACELIFT,
New paint with top clearcoat quality,
MVP front lip,
Big brake kit front - EU rear,
Rolled fenders,
Deep dish wheels (Work Meister, CCW, TE37 SL, ...),
ENGINE :
Refreshed VVTI 2JZ-GTE with single kit,
New oil/water pumps, ...
New FMIC,
HKS BOV,
FLUIDAMPR pulley,
STAGE 2 cams,
DRIVETRAIN :
Definately the TREMEC T56 (stock version),
Aftermarket diff (OSGIKEN),
SUSPENSIONS :
KW or other top quality brand (have to investigate a bit more this).
ELECTRICAL :
Syvecs S7 with toucan with all the features (launch, traction control, oil pressure alert, water temp alert, ...)
Excepted from the gearbox, wheels and suspensions, that's where I am with my 2002 N/A Supra.
The last year of production for a "modern" MKIV Supra is also important to my eyes =)