After some no.1 rimfire time, I feel that the offset firing pin in the breechblock is the way to go. Just my own opinion there. If the lifting arm is shortened, one has to keep the geometry proper as the breechblock has some surfaces to worry about when in locked condition. One can get vertical movement if not done correctly with the short breechblock lifting arm.
If one considers movement of the firing pin within the breechblock, one would suspect that there is a fixture to drill the firing pin cavity from the rear of the block. Using a 0.1" nominal shim to lift the block in the fixture would allow the movement of the firing pin cavity(6 oclock hit on rim), and utilize the existing firing pin parts in total. This keeps the original locking design intact.
The existing centerfire ejectors do not have a long enough hook to reach a rimfire. The No.1 extractor has no support for the case. So support could come from an angled slot in the barrel just like most of the rimfires on the market now. The chamber itself would fully support the case during firing. One would suspect a new casting the ejector, but does not look too hard to do; as castings already exist and could be touched or just redone.
Some do like a full sized rimfire equivalent of the centerfire brethren. Once you shoot one, you will be hooked; just a fun thing to do. A downsized version of the no.1 for smaller cases seems out of reach, sorta a sales versus R&D money to me.
Just beginning concepts on those done before, nothing new in the above other than perhaps the fully supported chamber, but I am sure some done such too for safety concerns of the rimfire case in certain environments.