i haven't done AS history but i have friends who have done so (AQA as well) and from their view, it's a lot of content. i believe there is coursework, but for A2.
why don't you do an EPQ instead? it looks good( shows independent learning) and doing an extra AS could potentially get in the way of your A2 subjects which are more important. Also, most universities give offers based on 3 subjects, so doing an EPQ could benefit you more (it's well respected). The EPQ could be on history, which means you could do it on something that's a part of the AQA AS history specification, so you could talk about it in your uni interview if needed.
hope this helped