Are you sure you wouldn't rather ask e.g. Indus Falcon, War&Peace or Khafee? After all, I'm just a brainless wiki copy-paste keyboard warrior ...
These FACs are primarily being sought to
- patrol littoral waters
- interdict and deter maritime criminal activity, such as trafficking and piracy.
Some missile capability would allow these boats to double as anti-access and area denial (A2/AD) assets in wartime.
The first point puts emphasis on endurance and sea keeping. The second point more emphasizes speed, either of the ship itself or in the absense of that, of the 1 or 2 highspeed shipboats carried on board (i.e. good launch and retrieve capability implied). A rotary wing U(C)AV might also be usefull in that respect.
For the wartime role, looking at current ships, one can wonder if PN would opt for anything more than adding antiship missiles. To survive, a minimum of some anti-missile capable cannon system, in addition to a dual purpose cannon system. More MRTP-33 or AZMAT, or a combination could well fit the bill. The bigger MRTP-42 might also be an option, or RMK Marine FAC (see
https://defence.pk/threads/the-next-generation-ships.207590/). The latter does not seem to offer much different from AZMAT except higher top speed and longer range
http://www.yonca-onuk.com/yonca-onuk-mrtp-xx-fast-missile-boat-109-1-urun
http://www.rmkmarine.com.tr/en/the-fast-attack-craft-_fac_-project.html
Personally, on the high end of the scale, I like Singapore's 1200 ton Independence class by ST Marine, even if it doesn't come with AShM (but it could easily house 2x Harpoon or MM30 size missile sets forward).
Alternatively, the similar displacement 75 metres PVs ST Marine built for the Royal Oman Navy: AShM but no SAM.
Also interesting (if seeking some land attack capability), the South Korean PKX-B
http://www.janes.com/article/62669/south-korea-launches-first-pkx-b-missile-craft