Before I gave some thought to making an Impaler similar to J. Boyd. (using a Bolt Thrower). I had made a couple before using different models but then this idea came to me:
How about just giving the Vulture Marksman Killing Stroke OR just making his Crossbow deal out x2 damage. If it does 12 damage then it does 12 x2, slightly less than the Impaler, and it does the same range as his normal Crossbow, though it could be raised three inches. Say a Crossbow does 21 inch range, it would then be 24 inches.
(cuz 23 inches and +2 inches would be sort of odd, though I suppose +2 range could work)
Lastly, give the Vulture Marksman +1 Wound.
In 2e he had 2 wounds, and that would mean he has 3 wounds, (and if it is 1e it means he has 2 wounds)
Why? because by then doing this your eliminating the Impaler from the dwarven army list. Your saying I won't use/have access to the Impaler at all.
I don't find the impaler imbalanced. The purpose of it is to get wounds early on in the game and because once you get within 10 inches the model is essentially ineffective and purely defensive, and the fact you sunk 89 points (almost 100) into it means it is not really that big of a deal. It is suppose to put damage onto a Soulflayer or take out a players caster who stupidly left it on top of a hill in plain sight. Yes it does have that 40 inch range. Secondly, a purely dwarven force can also be a slow force if you take certain units so this is a way for a player to reach out as they slowly advance and deal some damage. Keep in mind many spells have long range, deal damage and deal template damage, and have things like LOS range so really it is not that out of wack with such other options.
Still, many might not have an Impaler, and so I thought how about just beef up the Vulture Marksman a bit and it eliminates any over the top element of the impaler but also eliminates that downside of it not being able to fire within 10 inches and only being defensive too.
Even if you don't add the +1 Wound, adding that x2 damage to its Crossbow I think is the essential addition. Yes, that means raising the vulture marksman cost a bit, but clearly it would make an already great and useful model into something even more great and useful.
That is what I was going to do. I have 2 marksman and 2 firstborn marksman and yes I like fielding them. So that means you'd face at least up to two marksman if you faced me.
The other thing I thought about was what if the Impaler was "Limit 1 per 1000 points'