Ive come up with some ideas for if there will be a halo wars 2.
1. a phantom that you can train and use like an elephant but for the covenant.
2. If you trained a spartan he would spawn with a AR. if you selected him you could be able to have them hold a spartan laser, chain gun or a sniper rifle and there was not one that was the best. of course it would take supplies to give them a certain weapon.
3. being able to train falcons. you will be able to upgrade the gunner turrets to grenade turrets.
4. Because if they make halo wars 2 they will make it after halo 4, they should replace the cyclops with the mantis!
Thats all i can think of right now but post what you want to see in halo wars 2 here!