Custom GUI stuff has been criminally missing from Quake since forever, and I think it has stifled mod creativity.
CSQC in Quakespasm.
RMQ engine did that years ago and was actually based on QS. *cough* Spike did it separately as well, IIRC. It has technically been done for years, it's just that the community didn't really want it. Also, mods like Hellsmash definitely had custom GUIs. So does Brood Hunter. So did Scout's Journey when it still ran on the Quake engine. It had a friggin' drag and drop inventory (other mods did as well). Various mods by gnounc were all about custom HUDs. It's been possible for years, it has just been stifled by being "uncool".
There is even a cleancsqc source kicking around, also years old. https://gitlab.com/gnounc/cleanQC_merged
This thread is really funny to read. Suddenly you guys want volumetric fog, reflections, lightmapped water, custom GUIs, particles and all models remade. But Darkplaces etc. are still the Grand Evil. It all has to be crammed into Quakespasm instead of simply using a more capable engine. It seems the requests for features develop at the same pace as certain regulars' tastes (slowly).
I suggested switching fully to an extended (lightstyles...) Quake 3 map format, shaders and IQM models for PCs five or six years ago to the rest of the RMQ team and people looked at me like I was mad. It was mostly that mappers were unwilling to give up using Worldcraft (can you imagine that in 2017?). Instead we got BSP2, which is a hack, and lots of q3map2-like functionality (AO...)crammed into tyrutils lately.
It's really funny to watch.
These particles you always complain about in darkplaces could be fixed in a weekend if someone made a faithful particlefont.tga for the engine. That could have been done 10 years ago.
The cruddy SW-style lighting has been in FTE for years as well. AFAIK FTE got an entire "faithful preset" a couple years ago, even. Why all these things are slowly rotting instead of being used by the community, I fail to grasp. It really must be a comfort zone limitation. Or a pissing circle one.
You got a faithful looking engine with good Q3 shader support, RBSP/FBSP support, CSQC, and Quakeworld support, plus heightmap terrain and shadowless rtlights that don't impact performance too much, custom GLSL support even, and last I heard most of the bugs had been fixed, so what the HELL are you waiting for?
Does it have to do the dishes as well? (Spike probably has that prototyped already.)