And your comment about it being impossible to add the uncompressed textures back being impossible or a 7gb download? Im not sure how you came up with that figure. The original Doom 3 shipped on 3 650mb discs for the entire game... It would not take anywhere near 7gb to add the proper textures back. A texture pack bringing higher res textures to the game I would estimate to be at 500mb to 1gb. Totally manageable.
The problem isn't the size of individual textures or even the total size of all unique textures, it's the new packaging. BFG edition as is weighs in at 6.93gb so 7gb is a reasonable extrapolation, although true uncompressed high res would likely be a good deal larger again.
You may be interested in this - this guy over at Doom3world unpacked the .resources files and identified that the cause of this size was a huge amount of data duplication for each map. See: http://www.doom3world.org/phpbb2/viewtopic.php?f=40&t=25538&st=0&sk=t&sd=a&start=270
Of course it's nothing that couldn't be hacked around in code, but it seems unlikely to happen.
Note that I'm not even attempting to defend any of this, by the way.
The game was marketed as an improvement to the original.
It wasn't.
That doesn't excuse the degraded quality, but despite that I'd urge you to go back to the original promo trailer and work forwards from there, and see exactly what it was marketed as.