I agree with the rest of your statement, but the bolded part is not that easy. Yes, govt. can facilitate, provide incentives, etc but at the end of the day, its the foreign companies that has to decide whether or not they want to invest here. Govt cannot "bring" more assemblers out of the blue.
And talking about India, there's a hell of a difference. The reason you see so many companies manufacturing (and even exporting) is because of the size of the market. Pakistan sells around 1.25 lac passenger cars per year while India sells around 2.5 million....thats a 20 fold bigger market.
We already have 3 manufacturers in Pakistan. A fourth competitor cannot co-exist here but its only hope will be to ouster an existing one. Investing in pakistan means getting your share out of 1.25 lac cars(or on an average 40k cars per yr even if its extremely successful like Indus).
As a comparison (assuming for arguments sake that there exists 10 manufacturers already) in India, the 11th manufacture gets (on average) above 2 lac sales per year.
So who in their right mind would consider investing in Pakistan?