[purpleman]

Not sure if there's any interest, but I intend to compile a modified version of the latest Kodi and a modified vesion of MPC-BE that will enable the use of "resume playback" when using an external player.

I might look into making some more slight modification to support additional features. If anyone's interested in the details, I plan on enabling communication between Kodi and MPC-BE using file system (meta data files that will be automatically created and removed).

Open to more ideas or support.

I'd be interested in testing, for sure. I know it's probably asking too much but it would be great if you could find a way to have subtitles add-ons from Kodi working from within MPC-BE. I ask because you talk about "communication between Kodi and MPC-BE", thus raising my hopes.

Edit: feel free to contact me by PM for test builds, help, discussion, whatever really. I'd like to contribute as much as I can. 

I think that a dramatically easier approach would be to make it so that the subtitle feature of Kodi (and any plugins you have installed) are accessible from the context menu within Kodi (before playback starts) rather than from within the video player.
I'll look into this.