Here is a relatively simple idea. Rohan currently only has 1 recruitable heroic unit, the Royal Guard, and 1 other heroic unit that can be summoned, the Royal Archer. I think it would be very intuitive to merge both of these units into 1 through a mount/dismount function, similarly to the Black Riders, and increase the unit limit to 6. Most other factions have at least 2 recruitable heroic units, totaling 6 battalions, so Rohan is at a disadvantage with only 3.
For their abilities, they would keep their passive Guardians of Rohan ability regardless of whether or not they are mounted, and while mounted would have For Death and Glory, and while dismounted would have their weapon switch between bow and sword. This would make them very flexible and useful, and give Rohan both heroic cavalry and infantry, so that whatever style they picked, either infantry or cavalry play, they would have a strong unit to rely on.
Finally, I want to make a simple request that if you vote no, please post your reasoning why, because I think this is a pretty fair and reasonable idea. Thanks for reading