Let me throw some data at you to do some brain storming. I will mention Three Point of views to look at aircraft replacement for PAF, not just numbers. This is all food for thought. The replacement process may involve some or all or even none of below factors.
SQUADRON Line Up
For first point of view, lets go through a squadron line up.
Training:
No. 1 Sqn Rahbars K-8P
Number 18 and Number 20 are OCU squadrons used for training in F-7 aircrafts but im adjusting them under fighters.
Transport:
No. 6 Sqn Antelopes C-130
No. 10 Sqn Bulls Il-78 Midas
No. 12 Sqn Globe Trotters Airbus A310, Phenom 100, Gulf Stream IV
No. 21 Sqn Burraqs C-130
EW/AEW:
No. 3 Sqn Angels Saab 2000 Erieye
No. 4 Sqn Shaanxi ZDK-03
No. 24 Sqn Blinders Falcon DA-20
Fighters:
No. 2 Sqn Minhas JF-17 Thunder
No. 14 Sqn Tail Choppers JF-17 Thunder
No. 16 Sqn Black Panthers JF-17 Thunder
No. 26 Sqn Black Spiders JF-17 Thunder
No. 28 Sqn Phoenix JF-17 Thunder
No. 5 Sqn Falcons F-16C/D Block 52+
No. 9 Sqn Griffins F-16AM/BM Block 15 MLU
No. 11 Sqn Arrows F-16AM/BM Block 15 MLU
No. 19 Sqn Sherdils F-16A/B Block15 ADF
No. 29 Sqn Aggressors F-16
No. 7 Sqn Bandits Mirage IIIEA/DP ROSE I, Mirage EL
No. 8 Sqn Haiders Mirage 5VPA2/3 - PN
No. 15 Sqn Cobras Mirage IIIRP/EP, Mirage VPA,VDA,DR
No. 22 Sqn Ghazis Mirage IIIDF,IIIDA,EL,DL
No. 25 Sqn Night Strike Eagles Mirage 5VEF ROSE II, IIIDP
No. 27 Sqn Zarrars Mirage 5 ROSE III, VEF
No. 17 Sqn Tigers F-7PG
No. 18 Sqn Sharp Shooters F-7P
No. 20 Sqn Cheetahs F-7P
No. 23 Sqn Talons F-7PG
You can see 4 x F-7 Squadrons need replacement, then Mirage squadrons need to be replaced.
4 x Squadrons amount to roughly 72 aircrafts.
5 x Mirage squadrons are 90 aicrafts, these include specialist ROSE squadrons, which will be last ones to go,if they ever get replaced within next 2 decades.
1 x Naval Squadron -8th sqn - 18 aircraft.
Considerations:
1. So How many PAF squadrons can JF-17 replace?
2. How many can F-16 replace?
3. Should naval squadron be replaced by JF-17? or a completely new type of aircraft ?
4. How many more new squadrons should be raised ?
WING and BASE Configuration:
Now instead of squadrons, we can also go through wing to wing or bases. That might get too deep. But just have a look;
4 x Mirage Squadrons located at Rafiqui AFB under 34 Tactical Attack Wing in Shorkot
2 X Mirage squadrons located at Masroor AFB under 32 Tactical Attack Wing in Karachi
2 x F-7 squadrons are used for training at M M Alam Base under 37 Combat training Wing in Mianwali along with K-8 squadron.
The above configuration gives an idea that PAF may need to replace 4 Mirage squadrons with a Strike aircraft and since all are at same base (34 wing), so its possible that same type of aircraft has to be based there to replace all 4 squadrons.
Now can you speculate, which aircraft will be acquired by PAF that can replace 4 Squadrons.
Secondly, 2 x Mirage squadrons (7th Sqn and 8th Sqn)are based in karachi, out of which 1 Mirage squadron is dedicated for Naval role, flown by PN pilots. Second is used for attack role. There is another squadron (2 Sqn - JF-17) configured to support PN.
So:
1. Will this mean that 1 Mirage-V and 1 JF-17 squadron will remain in Naval support role OR will PAF give a third squadron to PN when it replaces the second Mirage squadron at this base ?
2. The Mirage-V squadron (8th Sqn) has only 12 aircrafts - If PAF gives an order for 24 aircrafts , would this mean that all 24 aircrafts can be used to replace these 2 Mirage squadrons and dedicated for Naval role only?
3. Should Mirage 7th Sqn be replaced by JF-17 and the 8th Sqn be given a new type of aircraft for Naval role.
Thirdly, 2 x F-7 squadrons are used for OCU role in a Combat Training Wing (37th Wing).
1. If PAF gets a new type of aircraft, will one squadron of that aircraft (lets say J-15) get based under this Wing ? And also what should happen to other F-7 Sqn ?
2. Should F-7 keep flying converted to LIFT role ?
3. Should PAF get a new LIFT aircraft ?
AIRCRAFT/SQUADRON ROLE
The third point of view is the role assigned to an aircraft or a certain Squadron.
MultiRole
No. 5 MR F-16 C/D Block 52+
No. 9 MR F-16 A/B
No. 14 MR JF-17 Thunder
No. 16 MR JF-17 Thunder
No. 19 AD/MR F-16 A/B Block 15ADF
No. 26 MR JF-17 Thunder
No. 28 MR JF-17 Thunder
Operation Conversion Unit / Multi Role
No. 11 OCU/MR F-16 A/B
Tactical Attack
No. 7 TA Mirage-III ROSE I/Mirage V
No. 15 TA Mirage III/V
No. 25 TA Mirage -V ROSE II
No. 27 TA Mirage-V ROSE III
Maritime Support / Tactical Attack
No. 2 MR JF-17 Thunder
No. 8 TA Mirage V
Air Superiority
No. 17 AS F-7 PG
No. 23 AS F-7 PG
Operational Conversion Unit
No. 1 FCU K-8P
No. 18 OCU F-7 P
No. 20 OCU F-7 P
No. 22 OCU Mirage III
PAF uses F-16 for all kinds of role, so inducts it in Multirole Squadrons. JF-17's 14th Squadron was Air superiority squadron but converted to MR after F-7 was replaced with JF-17, which means JF-17 is considered as Multirole by PAF. Mirage III and Mirage V are mixed in few squadrons as they compliment each other, but Mirage is mainly used for attack role where as F-7 is used in air superiority role.
Considerations:
1. Which new aircraft type ( new or used F-16 or J-15) should be inducted in Air superiority squadrons?
2. Should TA or AS squadrons be converted to MR squadrons if more F-16s and JF-17 are inducted ?
3. Should be PAF get a dedicated strike aircraft for TA squadrons like J-15 ?
4. Should PAF assist PN in raising a Maritime strike squadron or retain 8th Sqn for under itself for Naval support?
5. Should AS squadrons get assigned to J-15 or EF, if these are inducted ? what other choice does PAF have for Air superiority aircraft ?