Some UI mods don't load unless replacing the original files

Hello, I have an issue loading some UI mods. While graphics updates (textures, meshes...) seem to work fine once a data path is added to openmw.cfg, some don't load, like:

• Better Dialogue Font (http://www.nexusmods.com/morrowind/mods/36873/?), which replaces the font used in the journal;
• HD Intro Cinematic (http://www.nexusmods.com/morrowind/mods/39329/?), which replaces the cinematic introduction with one in better quality.

The only way I've found to use these mods is to replace the corresponding files in the game's original data.

I'm not sure if it's a bug or if OpenMW is currently unable to load data outside of the usual Icons / Meshes / Textures dirs (in the case of these mods, it's files in the Fonts and Videos dirs that need to be replaced).

Using OpenMW 0.41 from the PPA on Ubuntu Linux 17.04.

(RM-3886 from redmine: created on 2017-05-29 by abel thorne, , closed on 2017-05-31 by nobody)