As I stated - "Various ROMs" -
BUT NOT ALL - So it can't be the fault of the base AOSP but rather modifications done by Manufacurers or Providers (3 is the worst for customising)!
Not all ROMs are flakey or unfurnished and you have the options to customise them a lot more to your own personal style - Most providers add bloatware which slows the device down which a lot of people don't want (The only settings I need are for my APN)!
You can access internal memory via adb - but modifying it requires you to be rooted.
There is a fallback ringtone found within framework-res.apk which the device will use if it can't find any tones
at all but no different configs for SD in/out (Nice idea though!)
but copying to the internal memory would still require root!
This is where I benefit from a custom rom - If I don't like one then I choose another, or I patch the problem! (Or, more often then not, I just make my own)