I can't delete post, and now i can't even edit it. Unlucky.
Adding millions of new options, mechanics, etc. to the current roster can steal the uniqueness and expressiveness of unreleased content (items and characters). Imagine you want to give Vindicta the ability to see through walls (very bad idea!) by buying a "special item", this means that now if the devs want to add this ability to a new item or character, they will have to compare it to what Vindicta already has. Or maybe something more subtle, maybe a special item to add an extra slow to Paradox's time bomb? Well, maybe in the future there will be a character with an AoE ability that has a very strong slow but very little damage, but wait, the devs already made this slow in the time bomb.
I hope you get my point. But that doesn't mean I want to lock in the current ability sets. In fact, I think a lot of the ability upgrades are currently very lame and could use some tweaking, especially the early cooldown reductions. They could be replaced with some unique or interesting utility. Also, when the game launches, it needs to evolve further. This would be a great opportunity to add special items or something to the more established base.
This post is specifically addresses the "blue" item thread, as it's becoming too popular. But I also advise against anything like that for the time being.