I think right now making sure all 1898 and before firearms are totally exempt from Federal oversight is the goal
And exempting all muzzle loading guns.
I will say again that getting additional full autos permitted for civilian ownership, let alone having them exempted from fed.gov oversight, is IMHO way more than can be realistically done AT THIS TIME. It is a worthy goal, but why don't we expend our limited political capital on something achieveable and work from there. That's what the antis did, they got us one salami slice at a time...who in 1967 would've thought that we'd be where we were less than 30 years later? While I strenuously disagree with their goals, their TACTICS were brilliant.
My proposal, to simply update the definition of antique firearms (which aren't subject to any fed.gov regulation, a VERY worthy goal) is far more achieveable, and if implemented with an automatic update of the definition, will remove more guns from fed.gov oversight every single year.
After that we can go for other classes of guns. Believe me, I very much want to own several full autos, even if they're reproductions, because I just want them (Tommy gun and a Colt Monitor/BAR) - but it'll take time and a well-thought-out plan for doing so.
As for muzzle loaders, I'm all for your proposal. Even the antis can't demonize them too much, as the rate of fire is so low. They truly are antiques, even if made yesterday. I'm not into them, but I think that anyone who wants one or a hundred should be able to get it/them without Agent Schumckatelli sticking his ugly mug into the process.
Again, let's salami-slice the antis by expanding the definition of antiques first, and then go for other classes of guns later.