One of the few things the internet has successfully burned into my brain is that everything is a go'er to somebody. For some reason. Despite all logic. And reason. And what we normally consider to be basic humanity.
Somewhere on this planet there is a 14 year old boy obsessing over 2001 Pontiac Aztecs. Imagining himself behind the wheel. Writing newsletters for a fan club only he will ever join. Filling sketch books with pictures of himself touching every part of a Pontiac Aztec. If you try to talk to him about his obsession, to council him against it, he will dismiss you as a hater and complain that people just don't understand. Those who know him have learned to avoid the subject.
The up side to the 45/70 revolver is that you'll still be able to look down on and laugh at that kid.
The down sides are easier to identify. It is heavy, offers worse performance, is harder to down-load cartridges for, uses more expensive reloading components, may end up creating an unsafe situation in that you were asking about handgun rifle pairs and now you are talking about loading an old low pressure rifle cartridge to high pressures with pistol powder, and so on.
And, before someone takes offence: no, there probably isn't really anyone obsessed with Aztecs, even a 14 year old boy. I was trying to come up with an especially bizarre, even outre, scenario to illustrate the point. Even if there is such a kid, I realize that everyone passes through 14 and usually cannot be held legally accountable for their actions at that age. I find it is best to have a sense of humor about such things.