@Bevab I very much agree with your point about Rohit. He is really the player who gets on my nerves when I see him not effectively utilising his role. And I think he exactly doesn't score as quickly in T20s as we have seen in ODIs during the World Cup as he was the first player who took on the attack to the bowlers in the World Cup when he started opening with Rahul
The remaining 3 players I didn't mention should be Bumrah, Saini and Chahal as you mentioned above. So I have a lot of players in my mind the list would go as follows
Openers
Rohit Sharma
Virat Kohli
Shikhar Dhawan (as reserve)
Middle Order and All-rounders
Shreyas Iyer
KL Rahul (not sure whether he should open or be in the middle order, but for now I have him here)
Rishabh Pant
Hardik Pandya
Ravindra Jadeja
Washington Sunder
Manish Pandey (as reserve)
Spinners
Yuzvendra Chahal
Kuldeep Yadav (as reserve)
Bowlers
Jasprit Bumrah
Navdeep Saini
Deepak Chahar (as reserve if Bhuvi isn't fit)
Bhuvneshwar Kumar (as reserve if fit)
Other reserves (in case there are injuries)
(i) Batsman and All-rounders
Prithvi Shaw (if opener)
Shubman Gill (if middle order)
Shivam Dube (if Hardik)
Krunal Pandya (if Jadeja)
(ii) Wicket-keepers
Dinesh Karthik
Sanju Samson (if DK is not the option)
MS Dhoni (for extreme cases)
(iii) Bowlers
Rahul Chahal
Mohammad Shami
Khaleel Ahmed
Ironically we don't have any conventional off-spinner apart from Sunder so I think he becomes an obvious choice and his injury would really hurt the varities we have in Bowling department.
But good news is we have 26 options from which we can have our 15.