If you're reading this, you probably noticed the exclamation mark! Golly wow!
Okay, so here's my idea:
1. Go to vending machine!
2. Choose recipe!
3. WOW! You have all the mats needed!
4. HERE'S THE IMPORTANT PART! The machine allows you to give it ONE ADDITIONAL MATERIAL- That is to say, 1 unit of a material not called for in the recipe for the item!
5. You dump one of your materials that you have accumulated way too many of!
Now you hit the craft button and go to either 6 OR 7!
6. What's this? You didn't get the item you asked for? Oh, looks like you got a BRAND NEW THING that's kinda like what you asked for but has a different look, name, and traits!
OR
7. You got the item, but you get an INCREASED CHANCE FOR OBTAINING CERTAIN UVs, based on what material you put in!
Okay, how's that?
I quite like the idea of influencing UVs by depositing extra materials; not so much the getting-a-different-item thing. I can't speak for everyone but I'm pret-ty careful about planning my loadouts, and whilst there'd obviously be a chance of getting something better than you expected, there'd also likely be times when it messed with your whole setup.
Also, for UVs, it'd have to be very carefully weighted. I like the idea in principle, definitely.