The problem with the secondary runway is not its ability to handle WB flights but its ability to handle as many aircraft in an hour as the main runway.
It is a concern that the runway requires recarpeting so often.
The main issue is BOM normally handles about a thousand flights per day. Most passengers will not willingly fly the darkest hours of the night.
This will be slightly worse than the earlier in the year capacity constraints at DXB:
1. Longer duration
2. Secondary runway has less capacity per hour (as noted), due to taxi way layout, than primary runway
The link say 35/hour (vs. 45). So the prior configuration could handle 1,100 flights in a normal 14 hour operations of an airport with recovery capacity in off hours. The secondary runway can handle 490 in 15 hours, not even half capacity. 840 in 24 hours if there is no recovery from any delay +automatic cancelled flights). I've heard that an airport must use 25% to 35% of capacity to recover from off nominal opperations.
This doesn't bode well for BOM. It is a shame the new airport isn't yet close to being open to handle the needed traffic.