We've talked about this before, I don't line up perfectly with your (motorcycle) desires but I'm pretty sure BMW COULD build a bike that would work very well for both our wants.
All I'd change on your list is:
A. HP: 115 would be fine but, honestly, I'd be just as happy with 90 if the bike really weighed 520 pounds with 6 gallons (or, maybe 5 if the bike actually got 50+ MPG in the real world) of fuel and powerband was wide and smooth.
B. I'd want a bike that was a touring bike first and a sport bike second. I don't shred much these days.
The big problem, however, is cost. The bike we want would be cheaper to build than a boxer (opposed engines cost more than parallel twins) but I'm not sure BMW could get enough savings to make a significant difference in MSRP. Maybe BMW can cut cost with a non-German build location and a little "value engineering". Then we get to what will probably kill our dream bike, the RT barely makes economic sense now, cutting sales with an in house competitor wouldn't fly with the bean counters. The only option that would not steal RT sales would be an updated F800GT (much lower "content" like those advance rider aids) and we know that didn't go well.
FWIW, given all the audio I get with a helmet bluetooth and my phone they could save a bunch of money, bulk and some weight by dumping the whole on board music system. I would miss the satellite radio but I could live with that or mount a receiver in the tank bag. Just give me a couple of USB ports for charging. People who don't want music would save money and weight.
And yes, please, PLEASE stop styling bikes for young people who A. don't want motorcycles and B. can't afford BMWs and C. wouldn't buy a touring bike even if they are exceptions to A. and B. Its like they are marketing blow drys to bald people while ignoring people like me with a full (so far) head of hair.
These will sell even worse than F800GT did. What BMW needs is a T1000GT:
- Smooth parallel triple of around 950cc (hence the T) w/ 115HP
- Belt driven w/ 50K mile change interval (efficient, no maintenance, clean and most of all lightweight)
- All the performance tech of RTW: ABS Pro, Shift Assist, ASC, Ride Modes. Leave out the audio package, Hill Start, central locking, etc, to help distinguish it from the uber luxury ST models.
- All the comfort tech of RTW inc electric windscreen, trimmed but effective fairing, lighter weight panniers, heated seat/grips, TPM.
- Curb weight fully fueled: 520lbs including empty side cases.
- Styling emphasizing sport, but supportive ergonomically of distance touring, like RTW is.
Most all aging riders will appreciate that it would be as capable as RTW as an ST, but w/ 100lbs less weight. This would be the only bike I would change to in the BMW line and I fully expect if done really well would command enough market share to justify itself. Nothing exists like it among any brands currently.