Just take a prepaid airconditioned taxi from the basement. They're tiny for 2 pax plus bags, but fine if you're alone.

I don't really find Uber convenient from BOM T2. You have to walk in the non-airconditioned heat to the parking stucture and now they charge a INR 100+ fee for pickups from there, so some of the drivers don't want to pay it and try to call you to meet you outside, which is obviously a problem if you have an international phone number and don't want to pay the ridiculous roaming charges in India.