Most CAE grads join Kamra or become aircraft engineers in commercial aviation. The private market in Aerospace is limited to some UAV manufacturers who are mostly into copying designs rather than producing indigenous ones. So it is not too interesting as our neighbour. Forget the SLVs and all in Pakistan.
It might be good to go for Mechanical where you can cover some courses on Aerospace. You can do optionals such as Aerodynamics, Propulsion, CFD etc. If later on you want to do your postgrad, you can probably try for MS in Aerospace and that would be a better choice.
But if you are looking for a future in Pakistan - while most don't want to - best not to go for Aerospace. Having degree in Mechanical will help you make career in both aerospace as well as non-aerospace industry, that's for Pakistan. But if you are stuck with Aerospace, you will get to face limited job market, and in our "lakeer ka faqeer" system, your PEC Aero reg number owing to degree in Aerospace will not help you get into the broader public sector job market where the eligibility with PEC is "Mechanical" only.
Note: Kamra, NESCOM and other public sectors mostly hire Mechanical and Aerospace for same position.