Seems unlikely. Especially since power windows, locks, etc are all standard even on the base Mustang, it would cost Ford MORE to remove them. Since all those features are on the base model, Ford would have to tool up special manual window door panels, manual window crank mechanisms, etc, and make the adjustments in the assembly process to have these new parts installable inline with the standard cars. The spoiler is already deletable, and the front end, while different, is probably the same cost to Ford as the base model front end (except for the foglamps, which probably cost Ford $5 each.)
The 'problem' with a 2005 "V8 LX" is that the new GT really doesn't have a lot of non-mechanical content over and above the base Mustang to delete(thankfully!), so I don't see where Ford could offer a "V8 LX" for significantly less. By far, the biggest expense to Ford of the GT (vs the V6) is the engine, transmission and rearend, which, of course, would all have to be present in a "V8 LX" version too.
If you think about it, the GT *is* really more comparable to the LX of the previous generation, since on the 2005 GT, Ford (very wisely, in my opinion) decided to do without all the extra body cladding and such as was found on some FOX-generation GT's. Put a base 2005 GT and base V6 model side by side... they are VERY similar.
Just my 2 cents worth...
-Kent