Living: Andras Schiff: His playing has an impression of Chopin, somehow... He seems like a great person.
Dead/ Recorded: Rachmaninoff: I believe it would be great to meet him, and talk not only about piano, but also about the problems he went through in his time, and his stories.
Dead: Bach.
I don't know whether you live in Britian. But i noticed you mentioned Andra Schiff - he's doing some more "Beethoven Sonata cycle" concerts in the next concert season at Birmingham Symphony Hall - I can't wait to see them. Get a "International concert season" brochure from Bham Symphony Hall - the CBSO are also doing tons of concerts with such a variety of concert pianists this year. I've been away from the Birmingham area for the last 3 years so this is the 1st time i've looked into the classical music scene properly and there's soo much happening! Have a look:
https://www.necgroup.co.uk/visitor/symphonyhall/The great thing also about Symphony Hall is that students and under 25s get tickets half price or you can get "standby" tickets on the day - for students/under 25s they are only £3.50! So cheap (depending obviously if there are some seats left), plus if you're lucky you may get a really good seat on the day for £3.50 - which would have originally been £12.50/£17.50/£22.50/£26.50/£32.50/£36.
The following pianists are appearing in the next concert season (if you're lucky you might get to see them for £3.50

I know i will be at most of them):
Celebrity Recitals series: Aldo Ciccolini, Emanuel Ax, Andras Schiff, Murray Perahia
CBSO related concerts/piano concertos: Freddy Kempf

, Alexander Melinikov, Joanna MacGregor, Imogen Cooper, Peter Donohoe, Stephen Hough, Leon McCawley, Simon Trpceski, Boris Berezovsky
Other international orchestras/piano concerts: Jean-Philippe Collard, Denis Matsuev, Andrea Lucchesini, Freddy Kempf, Alexander Korsantya, Alfred Brendel

Lunchtime/chamber music recitals at CBSO Centre: Freddy Kempf, Benjamin Frith, Pter Donohoe, Leon McCawley
Such a fantastic range of pianists and orchestras! I'm so excited about going to all these. There's nothing like live music.