Items in the game need to be replaced very often. Stuff you find in chests doesn't come close to being enough to keep a party of 4 outfitted, so shopping trips are mandatory. It's already time-consuming enough having to compare several different merchants all over the place to find the items we want. And you think it would be a good idea if 8 out of 10 times, the randomly generated item would be 1-4 levels out of date which no one would ever buy?!

To prevent thievery? Even if you steal an awesome item, it'll be outdated in two levels. Whoopie.

Your merchant change will actually screw over legitimate players worse than thieves, which is exactly the opposite of what your goal is, which is to make thievery so annoying and tedious that the consensus will be to not bother with it at all.

So yes, I fully stand by my statement calling that idea idiotic, because it is.