I think there is one called the Hagn but like the Blazer very very pricy.
On converting a Ruger #1, I have no doubt it could be done but by the time you were finished you'd probably spent about enough coin of the realm to buy the Hagn which is IIRC, a falling block action. And, yes I would like to one of my very own, nuff said? Probably one of the biggest problems would be find a way to make the extractor work with different case head sizes. Guns like the Hagn have the extractor on the barrel assembly.
If you haven't noticed, Mauser is making the M98 in a sporter again. Check out he sticker price on those. Basic starter rifle is IIRC, $9,000 and goes up from there. The picture of the sporter frankly did not impress me.
I never did like the idea of switch barrels. I have a Savage M99 that has .22 HP, 25-35 and 30-30 barrels and I was able to also find a .303 Sav. barrel that also worked on the gun. Accuracy was not all that good even though the barrels were a tight fit.
You might try over on 24 Hour Campfire and ask Mule Deer (John Barsness) on the reliability of the break open guns. I believe he has a Merkel in .308 and has had nothing but good to say about it.
Paul B.