Here's my opinion on how reasoanble it is to want these things. Just my take:
Realistic damage that's better than what we've seen so far in other games.
Well the kind of set theselves up for this with the video of the subaru damage.
Mechanichal damage with the ability to blow tires, gearboxes, engines, brake fatigue, etc...
With the exception of the blowing tires, this is all reasonable to simulate to a point a few games have done this already. As for blown tires, I could see it as doable and reasonable from a programing perspective, from a gameplay perspective I think this could just be a frustration really fast as there is often little you can do about it and really who want's to simulate a failure you can't prevent?
More than 1000 cars, only a handful of them been on previous GT's, most of them new.
I am not sure exactly how this brakes down and how many cars there really are that would even be appropriate for this type of game so reasonableness there is questionable. In terms of time given to research, model and create these cars... doesn't seem unreasonable considering how long it's been underway
Porsches, lots of them.
Only reasonable in that anythign can change in the world of licensing but unreasonable in the likelihood it's really in PDs control
Revolutionary online system, with realistic slip stream, realistic collisions.
Not sure why this is unreasonable other than the fact that "revolutionairy" is a pretty broad concept. Forza did online pretty darn well, but I don't see how it can't be one upped.
Enhanced carrear mode, longer and better than GT4. More and better license tests too.
Again considering time to do it, not necessarily unreasonable.
Dynamic weather, with different types of rain, temperature affecting grip values, etc...
This one seems tricky and I would go so far as to venture had they shot for this from the get go, quite possibly doable, but to add it in now if they haven't planed for it so far, that coudl be very tricky. Also a lot depends on how accurately you want this simulated.
Custom liveries, "better than Forza".
Don't see why that can't be done... you see whats out there, give the same abilities and then some, maybe improve the user interface...
Telemetry.
If this is refering to telemetry like the stuff you can see in Forza about wheel grip levels and tire temp etc, I don't see why not
Lot's of DLC planned.
Somehow I don't see how GT won't have a fair amount of DLC
Bathurst, Road America, and a bunch of other new tracks.
Considering the time in development, I don't see why this is unreasonable, it's mostly just man hour dependant unless licensing is in the way.
F1 cars.
Seems like a licensing thing to start, then how accurately they want proper openwheel cars portrayed.
Skidmarks, rear lights, "4D" real time deforming trees and all that other minor stuff people moan about.
Skidmarks seems very doable, reverse lights I have no idea why they aren't already done, and I don't know if super realistic trees are necessarily what people want, but maybe things that don't stand out so obviously in an otherwise very detailed and good looking world. I think it's the contrast more than anything between gorgeous cars and cutout trees that gets people
Pace cars, girls holding flags at the start and other things to improve the overall experience.
I would think pace cars are doable girls with flags... I dunno seems doable but that's really more a question of appropriate for the kind of racing
20 locations being one for each country and one being PD land. 70 tracks are unique, not counting reverses.
This would be more PD's and KY's fault for not being more clear on the subject than anything, but again, doesn't seem impossible considering how long they have had to work with and their previous resources to rely on, although quite a high order all the same
At least two new revolutionary features we don't know yet to have a nice surprise.
Rally point to point stages.
With a WRC license this seems like a normal thing to want and expect
WRC, SuperGT and Nascar 2010 cars and drivers.
Cars I can see, I am not sure about drivers as GT has never really been about providing drivers... you are the driver
Full implementation of those series.
If licensed I think it's reasonable to hope that the series is done justice
