First and foremost, the servers need to be fixed. That said, here are some suggestions I've gathered:

1. Barbed Wire - Laying down coiled barbed wire does not allow a soldier to jump or move over it.
2. Easier terrain movement - If a hill is one block high, we should automatically be able to move over it without jumping.
3. Concrete Blocks - With the rumor of Mortars and C4 being added, a special block that takes a few more hits to destroy would be great.
4. Vehicles - This could be easy to implement with the addition of the "Easier Terrain Movement" suggestion. Tanks would be awesome.