I already did majority of work to port this plugin: Blender 2.8x MDL plugin

I did few "design" changes, I rewrote how skins and skingroups are handled. Now you use Shader Editor for that. Previous solution where you had to select stuff in UV Editor etc. was super dumb.

Final piece that is not implemented is "animation groups". I mean... it kinda is... but better idea is to utilize Nonlinear Animation blocks to group frames.

This way we'll have every aspect of MDL loaded into blender, so you don't need this script thing...

speaking of which...

...I temporarily disabled script generation (text file representation of a model structure). I plan to do it with proper JSON, for people who really need it.

So... this is what we have now.
A lot of people use this plugin with no problems.

You can port it back to QuakeForge.
Credit will be appreciated ;)

Cheers! 

I'll probably maintain my fork still, but I'll probably get some queues from this, thanks!
Btw I'm not really doing anything for QuakeForge, just forking their initial code. I have my own roadmap for this, which might be more Hexen II focused. 

Does this generate the bunch of QC code necessary to map frames? :D 

But thats a good idea. When exporting is done I might add that in eventually. 

Alright, just in time for the Blender 2.82 export is done. Big thanks to @Khreator for giving a great insight into exporting issues.

List of features:
+ Export support
+ Support for importing/exporting multiple skins
+ Better scaling adjustments, eyeposition follows scale factor

This is still considered an alpha release. But it should be good enough.

For info, roadmap and download you can visit https://github.com/victorfeitosa/quake-hexen2-mdl-export-import 

for a long time now: Would it be possible to save a blender physics simulation as frame animated .mdl/.md3? 

Enable MDD export addon. Export your simulation to MDD. Remove the sim from the object. Import MDD back into your object. You now have all of your sim frames as separate shape keys, ready to export to .mdl 

Disregard that. It works fine without any of that extra voodoo, just export whatever straight to .mdl 

Then let's think about practical use cases.
First think that comes to my mind are death animations, sagging bodies.
Explosion debrie might also work out.
I guess anything fluidic is out of question, like a tiling wave simulation anim.

What else comes to mind? 

Flags, fire, chains, breaking doors, breaking walls, etc.