Waalaikum us salam,
What I could understand from your plan, you want to touch each area in limited days. In that case my preference does not work here which is ?WE SHOULD HAVE TIME FOR THE DESTINATIONS WHERE WE REACH AFTER A LOT OF TRAVELING?.
I would say, if you are cutting down the days you should cut down some destinations as well. You have to understand that when you gain height, your bike slows down and at some points, it literally cry climbing. In that situation you can not do anything, you have to give time to yourself and your bike to get relax.
1. Astore to chillam (52.6km ? Not less than 2 hours)
2. Chillam to sheosar (15.7km - Not less than 2 hours)
3. Sheosar to sakardu (67km ? Not less than 5 hours)
4. Naran to babusar top (65km - Not less than 3 hours)
5. Babusar to chillas 47km (Almost 1.5 hours)
Day 1. Islamabad to naran/jalkhad (Achievable. You can stay at Naran or Batakundi. Accroding to my information there is no hotel at Jalkhad)
Day 2. Naran/jalkhad to gulmit (Nothing is impossible if you have courage to ride in any conditions. Reaching Sost is achievable if you have no issues riding without day light because I think you?ll get evening on the way to Hunza and Sost is about 90km after Hunza.)
Day 3. Visit Khanjerab pass, hussaini bridge and stay at gulmit (As I said, nothing is impossible if you have courage?. You will be able to reach till Ataabad lake or Ali Abad in the day light if you start your day from Sost ?NOT FROM HUNZA OR GULMIT?. Then till Gilgit in dark)
Day 4. Gulmit to chillam (Achievable in daylight if you start your riding early in the morning and have breakfast at Gilgit and If you stay previous night at gilgit then you can easily reach chillam. But check with someone if there is a hotel for night stay at Chillam. I have no idea about it.)
Day 5 Chillam to sakardu (Till skardu you can reach in day light but It all depends on the weather condition in Deosai. If you could save daylight then visit shighar otherwise without daylight its useless to go shigar.)
Day 6 Sakardu to shangrilla, upper kachura and try to reach chillas if not then stay at juglot (Visiting Shangrila and Upper Kachura lake can take you 2 hours minimum and reaching from Skardu to KKH takes around 6 hours due to road conditions. And then it takes around 3 hours to reach chillas. I think there is no hotel for night stay at Jaglot but do confirm it from some one else.)
Day 7 Wapsi (From chillas till Islamabad, you can not reach in daylight as well because from chillas it will take around 5 hours to reach till babusar top. I think you will get evening near around Mansehra.)
Your alternative plan is more or less same as previous. You said you have to reach back on 8th day but your first plan contains 7 days. Why like that?
What I could suggest you is written below:
Day 1: Islamabad to Batakhundi (Start traveling early morning)
Day 2: Batakhundi to Astore (Start traveling early morning)
Day 3: Astore to Skardu (Start traveling early morning)
Day 4: Skardu to Gilgit (Visit Shigar in early morning, come back, take breakfast and start travel. Visit Shangrila and Upper kachura lake and head to KKH. Manage time with less stays on the way so you could touch KKH before evening. Then till gilgit there would be no problem on the KKH.)
Day 5: Gilgit to Sost (Start traveling early morning)
Day 6: Sost to Khunjerab and Back to Gilgit (Start travel early morning, leave your luggage at hotel and take your breakfast or buy something to eat on the way because after sost there is nothing for breakfast. It will take around 6 to 7 hours till reach back sost. Take your bag from hotel and leave for Gilgit. You will get evening near about Atabad or Ali Abad. Then till gilgit in dark won?t be any problem.)
Day 7: Gilgit to Batakundi (Start travel early so you could cross babusar before 4pm)
Day 8: Batakundi to Islamabad (start at normal time around 8 or 9 am and you will be able to reach Islamabad before night)
(Note: This schedules are mentioned without including any other issue e.g. bike puncture, long stays of 1 hour at pass by destinations like sheosar lake, ataabad lake, babusar pass, lulusar lake etc.)
Hope It helps. Let me know if you have any further questions.