I like the extra banner diameter, very simple and properly focuses on their martial prowess.
Not sure why they can't have a heavy armour option though, as they were the most powerful human kingdom on earth at the time, far wealthier than anyone else. They'd have had the resources. If the argument is that it just makes them like Uruk hai, I'd say that's just an artifact of the rule system that has variation limits. Besides, the Numenorians came first, chronologically
About the steel bow: my impression was it was a naval marine weapon, made of steel so it could be shorter than a longbow for easier use on ships, but as powerful. So I'd just treat it as a Citadel Guard's longbow option (treated as elf bow), costing 2 points with a max shoot skill of 4+). They were probably expensive to make, so an alternative might be to make it more powerful (Str 4, but range and mobility as elf bow), but limit the number of steel bows to 20% or less rather than the normal 33%. Then you could opt for normal bows at 33% if you prefer.
I was reading up some other people's research and interpretations for other game systems, and the consensus seems to be that Numenorians were mostly heavy infantry, using swords, spears and pikes (or maybe spears with something like the Easterling's Phalanx special rule), with some small amount of cavalry, for scouting and skirmishing.
Good ideas floating around
I hope GW is watching and does a well-considered revision.