Three Maths A Levels?

So I am going into sixth-form in the coming year and I'll be taking maths, further maths, chemistry, computer science and physics The maths and further maths a levels are guaranteed because I got an A* in the edexcel certificate back in January and I sat further maths in the summer with a mock of of an A*.

How likely would it be for the sixth-form to enter me into the CIE international a level in pure maths? Bear in mind the sixth-form is mainly AQA, OCR and the only one relating to CIE is the Cambridge Nationals Gcse but the sixth-form and the teachers know me well enough that I can self study rigorously and this shouldn't be as hard as taking a completely new subject because it is less difficult than further maths and a little more difficult than maths as well as the module content being extremely similar.

The only difficulty that I can see is that there is only one compulsory 'core' module before it gets into modules compared with two in maths so I will have to learn either mechanics or statistics earlier than I'll learn it in class.

However the pros are that if I do, unfortunately, drop F.Maths due to the workload , I can have pure as a backup of a more advanced maths a level. It's also good in that it is an international a level as I have some prospects going abroad for university. Plus if I start learning the pure content early, it'll put less pressure on maths and I shouldn't fall too behind in core two because I have already done most of core 1 in further maths gcse bar integration stuff that I am gonna cover in the holidays. Lastly, doing the pure modules will help considerably help in doing further pure in further maths as a lot of sixth-formers who dropped who had got A*s in gcse maths and further maths said that the course was too dense in the content.

So should I pursue it? If yes then how should I go about it in the sixth form: maths teacher or exams office? Or is three maths related a levels a little excessive?