That is indeed a slick rig! Best of both worlds for sure. A set of QD rings, a Leupold 2x or 1-4x, and you're all set.
OP, I don't know how much you have played with the Skinner sights, but a receiver sight with a large "ghost-ring" aperture works really well for hunting if you are willing to put in some time with it. It's not like a scoped rifle (that is pretty intuitive), it takes some practice. I'm going to assume that you have a few .22's (don't know why I think that...

), so why not fit one with an aperture similar to what you think you want on the .45-70? That'll give the a chance to practice a lot for cheap, and the skill will transition seamlessly to the big rifle. I have a Marlin 39 set up that way specifically as an understudy for my .45-70 levers.
Make sure you aren't consciously trying to center the front sight in the aperture. Just look through the ring, put the front sight on the target, and squeeze off the shot. Again, takes some practice, but this method works best and is what makes the aperture sight so fast and useful.
If you aren't already familiar with it, look up the Marble Bullseye sight. It's a leaf sight that simply replaces the standard rear sight, and gives you many of the benefits of a receiver-mounted aperture while remaining very unobtrusive and low-profile. Quite inexpensive, too. I have this sight on a few levers and singles and like it very much.
And...be realistic in your expectations. A peep sight will work much better for your eyes than any open sight...but it will never be as bright, as quick or as effective in low light as a low-power scope.