[hac_]

What I'm missing is the option to somehow see and pick the used playlist when playing back Blu-rays in folders using index.bdmv. This is a problem in the few cases when the disc uses obscured playlists or has interactive version that is longer than the normal movie.

As the quote above discuses, I'm also unable to get DSPlayer to launch from a specific .mpls file when the title uses obscured playlists.

My workaround is to launch MPC-HC as an external player via playercorefactory.xml when selecting an obscured playlist title which works beautifully (I had to add mpls to "rule filetypes" for it to launch). I can choose to use DVDPlayer or DSPlayer using the "play with" option for other titles (long pressing w/remote), although DSPlayer will still not launch unless I have System>Settings>Video>Discs>Blu-ray playback mode>Play main movie selected, which defeats the purpose and doesn't allow for playlist selection with MPC-HC.

I'd also be interested to know if this could be fixed or added and if this is possible at all. Sorry for what might be dumb questions. Thanks in advance for any help or suggestions anyone can give...

I managed to hack together a workaround that seems to work quite nicely, but requires bit more configuration than yours to work.The negatives are that resume or automatically marking movie as watched when playback completes does not work.

In short, this uses a custom script as an "external player" which redirects Kodi's playback of the index.bdmv into the wanted .mpls file by controlling Kodi through the RPC interface.
Redirecting to correct playlist can be done by either dropping a <playlistnumber>.srt subtitlefile in /BDMV/PLAYLIST folder. This will also use that SRT-file for subtitles if you are like me and want a smaller font than what the PGS subs offer.
Another option is to drop playlist.txt to the /BDMV directory with the correct 5-digit playlist number as content.

I originally planned to modify Kodi source to improve the blu-ray playlist selection but I couldn't get the compilation environment configured in my desktop, so I gave up and went with this script since it works well enough.

I added the scripts and necessary config changes to pastebin if anyone happens to want to try this solution.
.bat file: http://pastebin.com/wH2XpLjw
python script: http://pastebin.com/v44N0UPb
playercorefactory.xml: http://pastebin.com/r9MhYcR8

Requirements:
Python 2.7.x with xbmcjson library
In Kodi, enable "Allow remote control via HTTP" and set same port, user and password as your python script config.
In Kodi, enable "Allow remote control from application on this system"
In Kodi, set "Blu-ray playback mode" to "Play main movie" - This makes Kodi start playback with index.bdmv file which we can easily identify in the script.

Additionally you need to edit under Kodi/system/players/dsplayer/mediasconfig_internal.xml and add mpls to the first rule:
<rule filetypes="mkv|avi|divx|ogm|mp4|mov|m4v|flv|m2v|mpeg|mpg|mts|m2ts|vob|bdmv|ts|mpls">

Would be nice if Aracnoz would add "mpls" to DSPlayer mediasconfig, it's the only change I need to do in the application "code" itself. Blu-ray mpls files play back without any problems in Kodi and DSPlayer, I don't know why they are excluded from the list in the first place.

I don't provide warranty or support with my hacky scripts