dH brought up the idea in another thread and I really liked it. I have thought about it since then, and talked to a friend of mine who is a good foil for ideas about it. I am still undecided as to whether to include them or not, but the discussion needs to be had.
Since dH mentioned the idea, I have started liking the idea less and less: newly designed (or radically changed) units are the hardest to balance, among other things. That said, I think it has merit, and should be tried, or at least discussed.
First of all, these guys are not in the Rare section because I think they better compete with Outriders, Pistoliers, and (to a lesser extent) Inner Circle Knights and Greatswords. Sort of like the elites of our shooters.
The fluff behind them would be (basically):
They do field testing on Engineer experimental weaponry, because those Engineers are too wussy to go out in the field themselves. They gather data and test the modern hand-held blackpowder weapons that are being developped.
-What I envision is almost a 40k-like small squad with different weapon options and BS4. The unit size would be 3-5.
-Your basic handgunner marksman costs 8+5. He can be upgraded to have repeater handgun for +15 points. Therefore I think the Engineer teams would be reasonably priced at 32 points a model, if they are skirmished, and have repeater handguns and pistols.
-Now, at such a high price, they are going to be a shooting magnet. Either we accept that and embrace 'fragile but dangerous' as their motto, or we give them some resilience. I am thinking of providing them with
--a) heavy armour
--b) 2 wounds
--c) full plate (probably too much)
--d) a 'dug-in' or 'pavise' kind of rule, which gives them a -1 to be hit (as if they were within 2 inches of the edge of a forest) and templates only hit them on a 4+ If they moved from their starting position then they would lose this.
We would have to adjust their points accordingly.
Weapon options: all the experimental weaponry, including a repeater pistol for free (in exchange for their repeater handguns). with the exception of pigeon bombs. Under no circumstances do I think throwing 3 templates of S4, range LOS, around is fair for a special choice. Not even 1.
The costs of the upgrades: probably the same for those of an Outrider Marksman. However, each model would be upgraded independently of the others. Hence, you could have one Hochland Long Rifle, one Repeater Handgun, and one Repeater pistol+pistol, or three of any of the above.
Also, instead of trading away their Repeater Handgun, the Engineering Special Team (or whatever better name we come up with) could select additional weapons (Repeater Pistol: +10, Hochland Long Rigle: +20, Grenade Launching Blundarbuss: +15).
They could purchase experimental flaming ammunition (/incendiary ammunition) at +3 points/model.
One may be upgraded to a champion with BS5 for +7 points.
I realize that at that point cost, if Repeater Handguns are kept, then a unit of 10 handgunners is strictly more effective, points to shot-output. However, the special team, being skirmished, is harder to hit, and has 360 line of sight. Furthermore, they take up less space, and are more versatile (you could have them as pistoliers on foot, for example... putting out 12+ pistol shots.