These are just some idea I thought of hope you like

1. Make Harvestors and some Refinery that it can drop it off (Balanced Some how)

2. Vehicles in general (I know this one is probly quite hard)

3. Playable/Reserchable Scirn(Maybe trade all pawns for a Drone Hive?)

4. More Scirn Units(As many that can be balanced)

5. Forgotton Faction(Just whould be cool)

6. Playable/Reserchable Forgotton(Just Whould be cool)

7. Super Weapons(Big Balance Issues)

8.Tiberium Being slightly more Volatile so you can make it go boom(Edit: Just Found out it is all ready added)

9. Tiberium BOMB(Massive Balanice Issue)

10. Some weapon to kill Tiberium maybe slow but still kill it

Edit: 11. Normal Faction Sieges be done still when tiberium is there and veins etc(had a normal faction attempt to siege me and kinda just killed them selfs on the veins before they even did anything)