Indeed, those nipples come in all sorts of configurations, some are very open, way open, too open. But...I sure would never replace a musket nipple with a #10 nipple, unless I didn't like reliability.
I completely understand not wanting the wood close to the nipple to burn out. (but not turn-rings) That does look like an especially open musket nipple, and much more blow back than normal. You can even get one that does not have a flash hole much bigger than a #10, but I'd sure prefer the much greater power of the musket nipple over a #10. Yeah...look into that nipple, and then shop around.
You know, I have a really nice 1861 Springfield, with really nice wood, inletting, fit and finish, and I keep an eye on that area, but don't really get any burn. I'll have to pull the nipple and look, but I'm pretty sure it has a fairly small orifice.
I don't think I'd bother installing a plate either, that one rifle "came that way". But I like it. Yeah I'd wind up boogering it up trying to do that. A super gunsmith/builder like Birddog6 could do it easy, in his/their sleep. One could get real fancy with it...!
But yeah, what EC said. (but not about the #10!!!)