Just a few thoughts I've had in reading the last several pages:
1: the porsche 968 Turbo S used a pump/cooler oiling setup to wring the last bit of strenght from the VW designed rear transaxel for the 400+hp tubo 3.0 I4 they'd developed. something you might want to investigate for ideas
2: a benefit of the separate oiling system for the turbo that nobody has mentioned is that it separates the turbo's oil supply from the dirty crap in the oil pan, and visa versa. so if one end fails from a bit of debris in the oil system, you dont loose everything. would also allow for two, smaller, oil coolers in different locations to keep the lube temps down. you are using an oil cooled turbo right?
3: on the intercooler side of things, has anyone considered using the CryoFuzion interfreezer? like the water/air, it is a limited use item, and would need to be paired with an air/air intercooler, but it might allow for a smaller intercooler, and the co2 purged from the interfreezer could be routed to a intercooler sprayer...
like you said, you dont plan to run it at 500+hp all the time, so at the lower boost levels, the normal air/air intercooler would do the trick.
(ps, I'm not talking about the DEI design, their exchanger clearly wouldnt exchange enough heat to prove worth while, even if it is less restrictive)
you could also add some N2O, as that would also cool down the inlet temps considerably...