I exported your .bsp to model with lightmaps, models are lightmapped: https://imgur.com/0hemZen
Even those, which you were not asking for :) This is known issue: > 1024 vertices push model surfaces to meta routine, which enables lightmapping.
Regarding to lighmapping quality (visible seams), this is general q3map2 problem. Enabling phong shading should help, also may be -trianglecheck for 'light bleeding' issue.
This should be improved once we get what's going on there, at least that 1024 limitation should be applied to separate surfaces of model, not a whole.

Loading folder with 137 512-1024 textures take a few seconds here, which seems to be realistic case for models. This is slightly too much imo, considering that models have to be loaded too.
I found some 50-100Mb models laying around in setup here. This is another topic, if to/whether it's possible to quickly evaluate if preview loading would worth the time spent/memory consumed. 

Got build with some working model browser:
https://cdn.discordapp.com/attachments/464535987993706518/703607488087457933/netradiant-custom-wip-20200425.7z
https://cdn.discordapp.com/attachments/464535987993706518/701421072611803146/unknown.png
That was a bucket of numerous small and big challenges there. 

Wow, very nice work!
Currently testing it, looks and works exactly the way i imagined.

The browsing through the model folders works fast and smooth, its nice to be able to rotate the models in the preview, and very cool to flip through those models with the misc_model entity selected.
Havent encountered any problems so far.

Anything specific you might want to have tested? 

It's good to know, that it works well with your practical cases.
Just tell, if something is not working, as expected.
I'v got a few questionable points:
-loading whole VFS here (root with max depth)(120k files) takes time, perhaps it makes sense to only load on 1st browser rendering
-there are some huge models laying around here, may be should load model file 1st to avoid loading, basing on the size (this is quite rough property tho)
-treeview expands quite widely and doesn't minimize, may be there should be draggable separator to adjust width and treeview itself scrollable horizontally 

Downloads are moved to github: https://github.com/Garux/netradiant-custom/releases/latest 

Wasn't aware until now of those -pk3 and -repack functions added to q3map2. Nice. 

hey niger, can we get a dialog so we can selectively unhide hidden brushes? 

There is list of all primitives, inluding hidden, on L, though i'm unsure how much usable the list would be for this purpose, i.e. how would you determine which entry of list is what.
I'd go around of it this way:
I, unhide, add brushes to selection, I, H
or:
I, unhide, add brushes to selection, region selected

More manageable way to control visibility should be likely done via layers. 

Hellzapoppin'! Roll up yer flaps and pick up yer brass, there's a new netradiant-custom build for all you hep cats and rug cutters, and it's a gasser! Those of you who've got yer boots on will need no introduction to this editor, but if you haven't yet collared the jive, here's the bible:

- It's hip.
- It's not for squares.
- You can cop it here:
https://github.com/Garux/netradiant-custom/releases