Crash:
No idea, sorry. And my mod doesn't change anything in the existing files, so if you're getting this error message even with my rulesets turned off, I'm probably not guilty
Nightly builds have their odds and ends, try using 1.0, or wait for the next build.
Hand Crossbow:
A nice idea, but it can't replace the bow - simply because it'd be very strange if soldier's Strength value was added to CROSSBOW damage of all things
And with the harpoon gun already in place, there's very little niche for it... Maybe a weaker, unlimited-ammo weapon... We'll see.
Tommygun:
True, there are many legendary firearms, and it always saddens me that harsh selection is required. The grease gun is both plain enough to be a good starting weapon and it works well as a weapon for Nazis and other scum like that. However, I'm not ruling the tommygun out (for the same reasons you've stated)... maybe as some higher-tier weapon.
Another problem with both ideas is somebody has to make graphics for them, and it requires time and effort
0.74 coming soon with several improvements.