I'm Sure Somebody Must Be Getting Tired Of Me Saying This.
But, detail brushes have been done in Quake. Firstly, the Quest compilers have them. They would feel incredibly primitive compared to aguire's tools however.
http://quest-ed.sourceforge.net/
If you have a PowerPC Mac (hah!), then there's a port of said tools with some added features:
http://quake.chaoticbox.com/downloads/equakeutils.sit
http://www.quaketastic.com/upload/files/tools/mac/misc/eUtils_r10.zip (same tools, just more compatible compression)
I'm guessing that Willem was looking at the source of one of these?
Finally, here's a fascinating possibility I found, from the q3map2 readme:
2.5.4 (2003-04-01)
- New: support for Quake 1, Quake 2, Half-Life, Unreal, and UT2K3.
On BSP/-light/-vis, use the -game argument: -quake1 -quake2 -hl -unreal -ut2k3
I have not tested this, and I don't know what it actually means, but there it is, q1 support in q3map2. If it could actually output q1 bsp format, and not just take it as input, then that would almost certainly be the best solution for cutting compile times.