[Flyndaran]

I believe weapons have loads of familiarities, and they're used more for disassembling than repair. ;)

I think one big issue is that Familiarities are like Fright Checks, very important for setting up the style, world rules, and details of character history.

It's also like previous threads on Mechanic tool sets. Realistically, they should be specific to not just TL, and skill, but also specific brand with one use items similar to real First Aid kits.
But that may feel overly restrictive to many gamers and GMs.

"Meh, close enough" probably fits Familiarities more than most other rules, I think.