SWR is planning to introduce the double decker Train between Bangalore to Mysore once the coaches are made available from Rail Coach Factory (RCF) in Kapurthala to increase the passenger capacity.
Air-conditioned double-decker coach are running on trials on the Delhi-Moradabad section a few months ago
http://www.deccanchronicle.com/bengaluru/double-seats-twice-fun-735
This should help passenger travelling between Mysore to Bangalore and catching flight at BIAL, by extending these trains upto BIAL. Trumpet Loop / Terminal of BIAL building.