What is the best short-term solution for fused neutrals?
I understand the theory of what you're trying to do, but I also understand the theory of the electrical installer that put fuses on both wires.  You still have a wire running through the house that is only designed for 15-20 amps even if it's the neutral that should be fused via the hot.  If there was ever a short that resulted in 25 amps going down the neutral, you could be looking at a dangerous situation.

My suggestion, if you want to fix it, is to go all the way and modernize the wiring with a full rip and replace.  Although the reason I avoid older homes is because I would end up ripping and replacing so much that it's cheaper to get the newer home (think insulation, wiring, windows, weather seal, etc).  And until then, if a fuse blows, don't assume the wires are safe unless you have personally removed the hot fuse.