Marines are expeditionary force or at least supposed to be in Pakistan's case. This means they should go places - beaches, deserts, jungles, mountains, snow peaks, riverine, swamps- basically everywhere. Even if they are k,ept as light forces meaning no MBTs or howitzers, they should still be able to perform multiple types of mission roles in different terrains. There was a talk of sending PA SSG into Afghanistan to rout TTP. Why wouldn't PM be a more suitable option ? In Pakistan's case, PM are on sentry duty. Protect shoreline, protect installations, patrol the swamps, provide static AD duties and in some cases assault ships if SSG (N) isn't in the scene.
In a practically ideal scenario, even if Marines aren't formed into a Strike Corps type of formation with armor, mech infantry, artillery, AD, engineers, signals etc, they can be trained on the lines of Army's LCB concept. Then they can be deployed all over Pakistan in company strength formations (100-150 troops) led by Lt. Comd. This would ensure that they at least possess air assault, CQB and AT training in their doctrine. These skills can then bring their name in all SF Ops which LCB performs.
Another thing, I opened a thread about Pakistan operating a foreign military base. It can be based in any friendly country however, its best suited in countries which have borders with India, e.g Myanmar and ports like Sri Lanka or Morocco or Malaysia. You see when you talked about forming a Marines Strike Corps, members here said that marines expansion or another Corps in Sindh isnt required, fair enough, it may hold merit, but remember Marines are an expeditionary force. Pakistan has stationed units in KSA. Pakistani forces didn't part in Saud-Yemen conflict but Pakistan could have sent forces to Turkey to form a military alliance. Now squeezing out troops from Army deployed in critical sectors like LOC, or borders isn't feasible. Some reserve formations are rotated for COIN war, a never ending war, at least the end is not in sight. Pakistan wont ever send Rangers or FC abroad, although they do go UN missions with Army. Its worth noting that KSA doesn't deploy troops in Pakistan except on training mission but Pakistan let USA take over Shamsi Airbase.
So if Pakistan expands Marines, where could Pakistan deploy them:
1. Rotation on LOC to relieve Army and NG battalions.
2. QRF on lines with LCB. in any cantonment or any city where Navy presides.
3. A military base abroad. Even in KSA to protect Mecca and Medina.
4. Sent out to any friendly country like Turkey to take part in Military Ops.
5. To conduct a military Ops in foreign/hostile country e.g. Afghanistan
