wow, busy thread.
Halkin I think hits the modern/cool/lux items you spoke about in your first post OP, but the bathroom and shower isn't very slick for a top level suite.
Rate point is certainly attractive
Four Seasons Park Lane is the location you are looking for over ten trinity... BUT I think 45 Park Lane and a London Balcony Suite will hit the modern/cool vibe you are looking for.
I'll also toss out The Stafford Hotel at Green Park as being super popular with Americans. Improved F&B now and the new carriage house 1 bedroom suites by Champalimaud interior designs are lovely (but expensive). The Mews section penthouse is actually a good value albeit it maybe a little dark in some of the decor as that section is already 10 years old.