I'd say thats a pretty good list. Give it a try and lets see how it works. Odds are your biggest problem with using this list is going to be you. When I first played with helmingas, I played the whole game rolling for wounds with S3 instead
So what I ended up doing is holding 2 different colored dice in my hands at all times, 1 color was for S3 units, and one was for S4. That way, I would pick how many dice I needed to roll, and was visually reminded to check for streangth.
Oh, and keep in mind any horsemen shot off their horse wont have S4, but odds are your going to place them down as a normal unit, so think ahead how you will tell the difference between a riderless soldier and a helmingas. (or make them a bowman that cant shoot? lol)