Mandarin Oriental might work. It's within walking/wheeling distance of Tokyo Station, and there is an elevator to the basement level of the Mitsui Tower which drops you off right by the Ginza Line entrance. Another elevator takes you down to the platform. From there you should have stair-free access to Ueno, Asakusa, Akasakamitsuke and Omotesando, and a pretty easy surface ride to the Ginza and Tokyo Station areas.