If you are staying in Pakistan then it's actually better to do FSC. Sounds strange, right? I never believed this when others said this to me. I thought, "Whoa, they are trying to mislead me. Do not believe them." But that's not true because Medical and Engineering admission tests for the top universities like GIKI, NUST, King Edward and AKU are based on Intermediate/FSC. There is little to no A'level content in them except for AKU's entry test which is a mixture of SAT II, FSC and a little bit of A'level on the side.
LUMS is the only A'level friendly university but it's too expensive.
In other words, it's damn hard to study FSC alongside A'levels. You have to put in a lot of effort to #1 get good grades in the CIE, #2 to prepare for the entry tests by studying the whole MCAT and intermediate syllabus.