An upgraded Y-9 platform is perfectly suitable if not better platform for ASW than a commercial aircraft. The P-8A was only procured after development issues with lockheed's P-7 which was an iterative improvement on the P-3. An ideal aircraft for a base for special mission aircraft could very well be a low mounted wing variant of the Y-9, which although fun to entertain is almost definitely not worth developing. I would love to see it though.