Gee, you don't say. Never? Could it possibly be that your players know that purchasing something like a Broom of Flying isn't worth it because you're going to add in a bunch of extra restrictions, and instead simply choose something else? Gee, shock.
I mean, think about it this way. No one ever says, "Oh, those new rules look really interesting and fun. I want to try those!" All they do is shrug and choose the thing that you're not going to nerf.
But, the whole point of this was never about the power levels of the items. That's not the point. The point is that the players will ALWAYS choose the most practical item. In your game, that means Boots of Flying because Brooms are restricted by additional rules. But, at no point around your players choosing lots of other flying items that might be less effective than brooms or boots, but are more interesting.
Which is the point I've been making all the way along.