Yeah as mentioned the 2jz uses sequential turboes of the same size, Toyota did this to gain low down power and anyone thats drivin a supra will also know around 4000RPM there is a drop in power when the 2nd turbo comes online.
Turbos have come a long way since the mid 90's tho hence the reason people put on big singles on the 2jz. A GT35R wont spool much slower than a stock sequential system on a 2j but will make alot more power.
There would be alot of R&D needed to make a sequential setup for a GTR, IMO money would be better spent on a 3L bottom end if you wanted quicker spool