To become an Emperor you must finish the Dark Brotherhood questline. Jarl Ulfric and Galmar can be recruited as your followers, and that includes officers and Stormcloak soldiers. If you side with the Stormcloaks you can still be an Emperor, but your home will be in Windhelm.
This includes every other Legate and solider out there. You can have Legate Rikke/General Tullius to be your followers. If you're an Imperial supporting Emperor your new home would be in Solitude. When you ask them to follow you they would respond back with 'Anything for you my Emperor' or 'I will protect you with my life, my Emperor'
I would add an additional following dialog to the guards. This is going to be a hard mod to create, especially since you will need to have some talented voice actors (Both males and females) that can mimic the voices of the guards and everyone else.