Yes, the main driver is cost. I have no doubt that Kibler has a very nice kit, but this is not the potential market of this gun. Kiblers kits are $1200 kit.
I aim for least expensive with US quality if at all possible.
I already ordered the prototype barrels and they are as lightweight as they can be for the caliber requirement.
I have no problem building a downsized gun, but it becomes an issue if you want to do it at a budget.
I agree with Ron, that this rifle/smoothy will probably follow a specific original style as best possible.
At this moment by analyzing geometry and parts requirements, it will probably look very close to a Mortimer Shotgun/rifle:
https://shop.davide-pedersoli.com/179-medium_default/fucile-mortimer-shotgun-a-percussione.jpgQuite straight "simple" buttplate, where originally built in flint and percussion, half stock, underrib, can be done with shorter rifled barrel and longer smooth barrel and look correct.
There will be some compromises necessary on the furniture: Those long pointy ends on the comb of the buttplate and on the end of the trigger guard will have to go.
As much as I like a checkered grip, this will of course not be possible at a budget.
Set triggers are not really a cost efficient option (adds $30 in parts alone) and are imho not required if the simple trigger is mounted correctly.
On the hooked breech: A cut of piece from a 1 1/2 x1 1/2x 3/16" regular A36 hot rolled square steel angle can be made into a tang by removing material alone. 60 cents material per piece with shipping included. Question is, how to remove material the quickest and most efficient to get to the end result.
Will probably require machining jigs. Tang will need radius that can be mortised with a 1/4" bit on a gun stock carver. Tang can be cold bent with a jig and press.
Hooked breech can be bought as is without the imho expensive tang castings.
Aside from bought parts, 2-3 hours of labor per rifle?
Parts from different suppliers directly:
+ Barrels with fitted hooked breech and machined dovetails? or cheaper to solder and dovetail sights/underlug at time of assembly?
+ underrib with soldered on ramrod pipes: soldered on using a jig
+ ramrod pipe cap similar than a traditions rifle with ideally hidden fasteners
+ commercial barrel wedge and barrel wedge escutcheons
+ butt plate from bent: 1/8"x1.75" flat steel bar: $2 Material, machining steps time unknown
+ commercial single trigger $10
+ Stock: 40 min on a radar carve? from 2" stock planks in cherry or unfigured maple
+ Locks: L&R Manton locks ($186 flint or $125 percussion + $16 sideplate in steel) or small siler locks (flint: $145 or percussion: $95 with matching side plate:$14.30
+ sight cost and underlug cost undetermined
+ trigger guard will be difficult for now