Not sure about how it would work as for entering you for the exam, but no, it's not possible as far as I know. For AQA AS and A2 Geography, you need to go on at least one or two field trips and to be able to write about what you did, why and suchlike in the exam. There's also loads of content in the other two papers where you don't do this, such as Plate Tectonics, Deserts, etc.
I got a B in Geog GCSE (OCR) but an A, 84.5% in AS (AQA).
Not possible is my verdict.