I applied for medicine and I did biology,chem, rs, maths and critical thinking but I then dropped maths at AS. The new course for RS looks very interesting but that means it is also it will be quite content heavy. Also, look at the modules you are doing as 1/2 of the A2 course for us was medical ethics which meant revising the ethics side for interview was suddenly a lot easier as all of it is lying in your subconscious. Choose which one you will enjoy and do better in as an A in one subject looks better than a C in another even if one is seen as more difficult as its still an A vs a C.
EDIT: one of the girls in my Alevel class didn't do GCSE. GCSE makes it slightly easier but only very slightly as you completely different topics especially in terms of philosophy