Jeff,
yes, the Hawken really is a difficult build, providing you want to do it right. Not one for a first time builder. The reason you see so many Hawkens around is because 95% of them aren't Hawkens.
I will chime in and agree with others, that you should look closely at some of the early guns. Many were converted to percussion in their lifetime, and you can plausibly build an early gun with a percussion lock. Christian's Spring, Edward Marshall, Issac Haines, Lancaster etc etc have all been mentioned. All of those will have a swamped barrel and balance nicely. They will all have a wide buttplate, making big loads more comfortable to shoot.
You mentioned not wanting to inlet a swamped barrel. A kit will do 90% of the work for you on barrel inlet. Don't worry about that. There is more to worry about than the barrel inlet.
And again, probably not a Lehigh. You won't like shooting a big bore Lehigh.
If you want it to be a gun that you pass down, don't do a Hawken badly. Do an early gun, converted to percussion, without much embellishment and do it well.
Jim Chambers offers percussion conversion locks, perfect for what you are looking for.
Cheers,
Norm