How about we don't put the cut in the rafter ....- we leave the rafter full strength, and instead make a slot cut into the top member of the top plate. Now the rafter partner will slide in. We can even add a rafter tie plate for more axial stabiilty and to make up for the slot we cut in the top plate. Home D has galvanized steel simpson nail plates
I've been making handcrafted repairs like that in the old farmhouse I described above, for the past 60 years starting from Dad handing me a dull yard-sale handsaw and hard-as-iron recycled lumber.
And continuing unbroken through last week's project: the attic is a simple guest bedroom with outdoor stairs. Entry is a regular door with a screen door outside that, which has plywood panels added over the mesh parts of the screen door to make it a more or less solid door. Somebody failed to latch that outer door recently. I found the door in five pieces. The hinge edge of the door remained attached, its other components had separated and blown down to the deck below.
Two partial days to patch the broken door structure with brass screws, add new plywood, then scab Simpson mending plates onto every intersection of the various members. Careful measurements to match the out-of-square door jambs that the door had been cut down to match. Prime, remount, paint. Good for another 50 years.
Why not buy a replacement door? Odd size. Frankly I'm tired of these hand-built repairs everywhere on a farmhouse that realistically should have been replaced years ago. Hence my advice to the OP to find a different house where someone worked his heart out restoring it instead of starting on this one.
I took the photo below for a different purpose, to illustrate the 3-point forks I made, but it shows the stairs to that attic room. Note the change in pitch of the roof? Originally steep, then the bathroom addition needed the lesser pitch for headspace, then finally the sunporch addition Dad and I built in 1960 needed both a step down into that room and a flatter roof for headroom. Still its exterior door is cut down from standard height to fit under the low roof. And that too-flat lowest pitch has been troublesome since new, each re-roofing has included replacing rotten plywood decking there. Old houses are a PIA. I keep repeating Dad's advice to my own kids - just bulldoze and replace, don't continue to pile patch upon patch. For the OP, find a different cute, already repaired, old house!