A suggested 15 days plan can be as following
Day 1: Leave from Rawalpindi at night by bus. Leaving at night would enable the travel on KKH in the day time.
Day 2: Reach Gilgit by evening. Night stay at Gilgit. If u desire and time allows, u can go further till Hunza and have night stay there.
Day 3: Reach Hunza early morning (or u would already be there on Day2). See Baltit, Altit forts etc.
Day 4: Trip to Khunjerab and back to Hunza (or Gilgit).
Day 5: Travel to Skardu
Day 6: Visit Shangrila and Upper Kachura Lake. Night stay at Skardu.
Day 7: Trip to Shigar and back to Skardu.
For Deosai, main question would be that deosai route is open or not at the time of ur visit. It would decide the program of next 2,3 days.
If Deosai is open, u need to do the arrangements for visit on evening of day 6 or 7. The main thing would be to book a jeep from Skardu to Astore. Other things would be taking eatables etc and arrangement of tent(s).
Day 8: Leave early from Skardu. On way to Deosai, have a brief stay at Satpara Lake and then continue. Enjoy at various landmarks of Deosai (Bara Pani, Kala Pani, Sheosar Lake etc). Leave Deosai at around 5pm and reach Astore. Night stay at Astore.
If Deosai is not open....
Day 8: Visit Satpara in first half of the day. Leave for Astore via Gilgit-Skardu road. If u dont find direct transport for Astore, then go till Jaglot or Gilgit, and leave for Astore early morning next day.
Day 9: Visit Rama valley and Rama Lakeand back to Astore for night stay.
Day 10: Go to Tarashing and visit Rupal valley etc. If possible, u should come back to Astore for night stay.
Day 11: Leave early for Raikot bridge. U should try to reach Raikot bridge by 12 O'clock. However, even if u reach by 2pm, u can still manage till Fairy Meadows. On reaching Raikot, immediately get on a jeep and reach at Tattu (last jeepable point on way to Fairy Meadows). Then hike for almost 3 hours till Fairy Meadows. Enjoy the beauty of FM.
Day 12: Hiking trip to Nanga Parbat Base Camp and back to FM.
Day 13: U can have an extra day at FM. However, IMO extra day is not required. so leave FM before noon and reach Raikot well before evening. Go to Gilgit and have night stay.
Day 14: Trip to Naltar and back to Gilgit for night stay.
Day 15: Leave for Rawalpindi by earliest bus in the morning, which would take u to Rawalpindi at night.
Note: The above plan is just an outline plan. U can add or delete few things out of it. Similarly, u can change the order of places to visit. But this is just a starter. U can start working and further keep on refining ur plan.