I think that you should do some market research. If you find that the majority of potential students would have GCSE french I would offer Italian to A2. Competent linguists who have studied French should acquire Italian quite quickly. I would do this because studying a subject to AS over 2 years would appeal to very few I imagine. I think that most potential students would feel that they were no getting enough bang for their bucks if all they have to show for 2 years study is an AS. By all means introduce Italian from year 9 as well and work up your numbers.