Go for it! Of the rifles listed, I'd go the the jaeger style as made by Christian Edwards. There is one major advantage of a shorter jaeger - they're shorter. When I finished my first rifle, I couldn't shoot it until I got a long enough cleaning rod. A forty two inch barrel requires a very long rod (I don't use the ramrod for cleaning).
The rifle I built for myself is left hand flint with a L&R lock, double set triggers, brass hardware and roman nose, inlaid fish (symbol of Christ), eight point star (so I don't get lost), acorns (I'm crazy), brass patchbox and a brass bleeding heart (Passion of Christ) on the wrist. Over a three day process, the barrel was browned in the garage.
Most of assembly is the woodwork and not being trained in cabinet making, I took a 6 day class offered by the Log Cabin Shop in Lodi, Ohio on how to build these things. John Plybon is the instructor and is very skilled and modest about his work. I'm now studying woodworking techniques under my uncle who is a cabinet maker.
Now I have to learn how to engrave - something I've been avoiding for years.
DZ, go for it. You'll have lots of fun and have a product you will be proud to bring to the range.