If an individual applied for Royal Marine Officer training and passed POC & AIB yet was not offered a place in the YO batch, would that individual automatically qualify to go to Dartmouth for Naval Officer training given that they have passed AIB?
I was informed that my score from AIB would allow me to enter as a warfare officer or as a navy pilot providing I took and then passed further tests. However, I had no interest in these particular career paths.
So in answer to your question I think it is possible and passing AIB does provide you with alternative options if you do not make the batch.
Like RMRO states I personally would not consider this as an option because of the difference in career paths, it is very different to an alternative sandhurst and becoming an infrantry officer.