I came upon this thread and even though you have good intentions vladax, you are better off re-designing MPC-HC or GOM or VLC.
Yes, Splash needs work. But the reason so many of us like it is for its SIMPLICITY. That's right. Sure I can easily use MPC-HC or XBMC, or GOM, or VLC, or plethora of other software, but Splash has its cleanliness.
Splash is a NO B.S. to the point player. It has its flaws, but a product is not better because of FEATURES, its better because of how well it implements the BASIC features.
Instead of polluting SPLASH interface and Front End, I think there should be a Seperate ADVANCED Functions and Features program that should be given that will allow the use of More Settings.
This way, BASIC Splash Pro will be there, and if an advanced user wants, they can use a secondary executable file which will allow changes to be made to Backend features that you mentioned, like subtitle handling, etc etc.
This however is probably a long way to go. I am sure the SPlash team is focused more on Fixing and bettering what they already have than to think about adding more Problems to their product.
The more features, the more Bugs and Problems. Its better to remain Simple. When you have a good product that works, you stick to making it better, not adding more and more junk.