can you modify the AIW so both left row cars and right row cars go the same way at the start of the race ?
No as far as I know the AI logic decide what actions the cars take.
All I can do with the AIW is define the track edge and 2 racing lines, the AI decide how to use and share the track. Don't forget that AMS is early access and improvements could still come.
You can experiment with AI tweaks...
slowwhenpushed=0.5 <<< try setting 1.0
AIBrakingStiffness=(1.0000,1.0000,0.9000) <<< you can tweak the last number a little bit and sometimes see a change in the AI.... (0.85 to 0.95)
AISpec=(0.0000,0.0000,1.0000,0.0000) // 4 ways to express AI speed on track, limit the acceration, max speed, their cornering speed, or their deceleration. 0.0 - 1.0
AISpec try 0,0,0,0 but I doubt this will change any thing. Don't get crazy with tweaking this variable its either 1 or 0 to notice a change.
Ensure you let the AI qualify properly so that the grid is sorted from fastest to slowest.
Try a rolling start behind the safety car... once you are rolling (you can) hit the space bar to skip the lap behind the pace car. This will teleport the grid to a point just before the final turns. Maybe if the grid drives the chicane then they will separate enough to make T1 without issue.
Set the AI aggression to low. Decrease the AI strength. Some times you get faster lap times and improved behavior from running slightly lower AI strength (just a few percent) it depends on the car type.