Special and Visual Effects : The scope and cost of large-scale practical effects today?

The scope and cost of large-scale practical effects today?

So, let's say I'm making a blockbuster tent-pole, and I've got 160-170 million overall (and a very faithful studio). Would large scale set-piece effects sequences, done practically, be allowed in this day and age, despite CGI offering a nearly-as-good alternative (and, funnily enough, a lot more practical to pull-off time and money wise)?

As an example: I want to portray an E4-B Airborne Command Post (never seen in a Hollywood film so-far I believe) with characters on board monitoring an international crisis, offering command & control, and then being attacked and barely surviving as the aircraft crashes into a highway intersection. Here's the clincher: I want to do it practically, for 100% photorealism. So I trawl the classifieds for a Boeing 747, and find an old one for 2.5 million, needs painting (a million or so), needs an airworthiness test (very expensive apparently) and needs stripping-out and everything replacing with a realistic set for my characters, to act in whilst aloft, not to mention mock-ups of all the real thing's external antennae (many, many millions spent here) and of course, official permission to portray this aircraft in a work of fiction.

http://img.planespotters.net/photo/268000/original/73-1677-USAF-United -States-Air-Force-Boeing-747-200_PlanespottersNet_268512.jpg

Now I need camera planes, fueling, security, weather analysis- and a special crew to rig the aircraft for remote control, so we can ACTUALLY crash it, and film it! Hell, I even want a few negative G shots, where the characters float in a panic for a few moments as the plane nosedives (the plane CAN do this).

So I take this proposal to the studio, and give them the puppy-dog look.

What would they say?

Those giraffes you sold me, they won't mate. You sold me queer giraffes.