Think about it...heroes and lords already have them. Why not take it a step further and allow unit types to do them also?
This can honestly solve the problem with banners, musician, Chaos Marks, etc.
You want a specific unit of Empire Knights to have the banner which gives you strider? Buy it!
You want a specific Chaos Warrior to have the Mark of Khorne for Frenzy ability? Buy it!
They need to allow the ability to save a certain unit loadout so that, in a pitch, we have a pre-built unit which the associated abilities already attached.
This would add a WHOLE new dimension to this game and I can see no real downside to this other than implement a much needed feature.
"Burn! Burn with the fires of Change! Scream your hymns to Tzeentch!"
-Tal'gatha the Fallen