The major problem seems to be the confusion between interior and dashboard view. That confirms that at least dashboard will be available for Standard cars, which in turn allows for Cockpit camera on all cars. 

Premium will have detailed interiors, thus the only ones having an "interior view", AKA, being the only ones that can actually be seen completely on the inside. On the official US gran turismo site, they added a note with Standard cars not having interior views.

It's not official. This source is not trustfull. We don't know yet if:

1-the cars will have cockpit similar to real life but not as detailed(like, only dashboard)

2-the interior will be all black in cockpit view(like in psp)

3-there will not be cockpit view at all for these 800 cars.

If option 1 is not a viable solution, I rather have option 3 than 2. Option 2 would be a serious stain in GT5

I wish I could take this as "problem solved" but I do not trust this source.  First off it comes from an Austrailian blog who originally stated the source of the information came from Polyphony Digital and then later edited their post stating the email came from Sony. Second, this is the only source stating this information.

I know there is a lot of people claiming that the standard cars do have modeled interors but it will be a "standard generic cockpit", but what does this meen? Then there is this quote which is supposed to clear everything up but only makes me more confused. "The developers have created fully modeled interiors for the Premium cars, as well as doing detailed modeling for the car's undercarriage and even the exhaust pipes! The Standard cars apparently won't have the exact interior modeling. For example, an Enzo's interior will look like the real deal, but your typical Mustang's will look like exactly like Mustang's." If someone could explain what that means I am all ears.

The truth is nothing has been confirmed yet about the 800 standard cars having modeled interiors, just opinions and speculations. 

I disagree, if option 1 is not viable, then I would rather have option 2.  I tend to like this view because it is the closest to being in the driver seat.

Unless you have a steering wheel. Then bonnet view is best. Having the real steering wheel in front of you, then another onscreen is completely detaching.

Interior views are nice and all but i gotta admit, i always race with just the dials when i'm actually going for a quick time.  But i can see me using the interior views during the early days of GT mode to get that authentic feel when buying new cars and such...  I hope mods are represnted on the cars too, but i guess we will have to wait to find that out.