I don't know why they didn't make weapon enchantments transferable.

Get a cool sword, but your character uses halberds? There should be something like if you have proficiency in smith's tools, you can spend a few days transferring the magical properties to the halberd. Do some basic rules about what types of properties can apply to what weapons and you're done. Simple.

Also means if there's a specific weapon that is important to your character ("This is the sword of Horace Greenhilt, my grandfather, from which my family gets its name") you can now just keep improving that rather than having it be replaced by the first +1 sword it finds.

Seriously how is this not a rule? Would take a few lines to save so much hassle.