They already put standard-definition materials on their BD releases. All the previous special features from the DVDs are on the Trek BD releases, and they're still in standard def, which according to you, shouldn't have happened since "they'd be duplicating content currently available that they're already trying to sell you". Most studios are doing the same thing.
Hell, even the Ultimate Edition Harry Potter films on BD include a plain old DVD of special features since they just ported pretty much the same disc over from the previous release. And Disney BDs include a full DVD of the film on top of the BD and digital copies.
Don't act like you're an expert on the home video market or BDs when you make obviously incorrect statements.
Yes, blurays often include bonus features in SD, almost always re-purposed from earlier DVD releases. We're talking about including a second copy of the entire show, over 22 extra hours of material. I'm sorry if you can't see the difference.
If a TNG-R were done like the TOS-R Blu-Ray, it would just need to have the seamless branching so you can choose to have either the original upconverted, or the new FX. That way, both people are happy, and you choose your version, but either way, it's still in HD. No need to argue that point.
Not possible. The original version of the show will never exist in HD. If they could just branch between the two it wouldn't be much more of an issue than TOS sets, but switching between newly restored film elements in HD and the low resolution analogue masters of the existing show would not be "preserving the originals."