The problem is that this pattern "pitch somebody something" is not recorded in any major dictionaries.Yes, it's correct. "I'd like to pitch a proposition to you" might be more natural. The idea is "present or offer, in the hopes that you will be persuaded to accept."
All I can tell you is that it's common usage in the US. The usage may be (in part, at least) borrowed from baseball. You don't pitch at a batter, you pitch to a batter.The problem is that this pattern "pitch somebody something" is not recorded in any major dictionaries.
Only "pitch something at / to somebody" is recorded.
I'm wondering whether in this context, "proposition" is a bit too formal to be used with "pitch"?WR Dictionary for pitch as an informal verb, #24:
to attempt to sell or win approval for something or someone by advertising, promotion, etc.,politicians pitching on TV.
(It's also very common in show business, producers pitching the idea or outline for a play, TV show, script, film, etc.)