Normally when I get a partial success for a mnv, I simple say it takes more time or apply a penalty to action for a length of time (normally one round).
For a craft, I say the object is done and whole, but is not pretty, or increase its break numbers, decrease its strenth, apply a penalty when it is used, etc.
As with most skill use in the game, I find GM fiat works best. I do not care for the reroll unless it really makes sense. Best to take partial success literally. You succeeded, but not as well as was hoped for or possible.
Same for near success, just smaller penalties.
BTW, this interpretation is how I came up with the orgin of +1,2,3,4,6,7,8,9,11 etc items, or spell enhamcers that are x1.6pp instead of x2. No way a guild is gonna throw away the apprentice sloppy work when it can still generate a profit off it, for sale or as a gift.
yamma