Having just got that visual c++ express thing to work, I had a little bash at getting fitzquake to compile, and then once I got that to work, I turned my eyes towards fiddling. First thing I tried was the model interpolation tutorial from QER(http://qer.planetquake.gamespy.com/news.html).

Fitzquake does the model drawing code a little different from standard GLQuake, so it took a bit of hacking to get it to work. Technical bit: Fitzquake eliminates the need for a variable called int lastposenum in the model drawing section, but the model interpolation code expects it and adds another one called lastposenum0. So I just added them back in, which isn't neat, but works...
It looks kinda pretty. r_int_animation and r_int_transform control the effect, default to on.

The other thing I messed about with was monster clip, people keep asking for it in their maps. Now, it would be a bit of a daunting task to put it BSP side, you'd need altered compilers and engines, and trying to do all this while keeping things compatible. So I went down the slightly easier route of adding a flag so monsterclip entities could be added.
FL_MONSTERCLIP = 8192;
Set this flag on an entity and it will only collide with entities that have FL_MONSTER set. This does exclude the world, so grenades with FL_MONSTERCLIP will fly through walls etc, it's intended for use with BSP ents.

The mod and map included demonstrate the idea. Walk through the big block of concrete in the middle of the map, it won't stop you, only the ogre. Won't stop his grenades either, beware. The block is visible for demonstration purposes, in a proper map you'd probably uncomment the line in the mod's code that hides the model. In theory you wouldn't even need a custom mod to achieve this, there's some kind of progs hack to make an invisble, solid BSP model right?

So yeah, take a look if you like, stuff can be found:
http://people.pwf.cam.ac.uk/~ajd70/fitzhack.zip