If old man Wagner was still alive I'd a been in charge of New York now!-(Death of a Salesman, playwright- Arthur Miller)
I'd a been in charge of New York now! Does this sentence means -- I would have been in charge of New York now!
Anyway pl. explain "I'd a been"
You are right: that's what it means.
It's sometimes punctuated I'd'a been – the apostrophes indicating where letters are missing.