Getting special preference for Tamilnadu bound trains at bangalore is altogether a different story. Many officials in SWR belong to TN and that could be one of the reasons.
For long time, SWR is serving different states. Just think UBL-SBC is not FEDL so far. Things are getting changed now-a-days and more intra state trains are getting started.
I...
more... think getting trains to Bangalore is easy via DMM route considering SR is not involved . Having said that most of the stretch (complete) GY-YNK is getting doubled, higher chances for introducing new trains. Again, something needs to be pushed at SWR to accept more trains. For example, parking trains at Chikkabanawara/Whitefield etc. It needs some pragmatic minds to think positively. Again, we also should think not all trains can be accommodated in the morning and leave bangalore in the evening.
Note: DHNE-GNT single line will still be a bottleneck