1. No dragons
2. No sweetrolls
3. Penalties for going all nude during winter.
We do get starter gear, it's all in the house you start in. Also if you need hardware supplies the warehouse or hardware store are always stocked with enough supplies, even if you are on rare. Also I love the idea of lockpicking.
To be serious my big three are
1. No hunting rifles or silencers, I want to turn my park ranger into a master marksmen
2. Lacking of generators
3. Not being able to do graffiti and make effective "HELP" signs or making custom landmarks to know where you are.
I'm sure all those will be added in eventually though and there is already a graffiti mod.
Oh actually I'll go ahead and add a fourth
4. NO BASEMENTS, I really want there to be basements, maybe even a few basements with left over bomb shelters in them.