My thoughts as a player...
1. You can't make magic items more "WOW" by making them harder to get. You just make it more frustrating. The only way to make them more WOW is to bash your players over the head giving them a case of amnesia where they forget having seen or heard of all the different items making them all brand new.
Actually, this is definitely not the case for all players. For example, I know one game where people do go wow at many items, but have no access to certain magic items. It's cooler than what they had, they weren't expecting it to be available, so when they get it instead of going 'Meh, maybe it's better than what I got' they go 'Ooh, I could use that!'
3. Disallowing the wizard from being able to craft items fairly easily messes up a lot with the design of 4e. The ease of crafting and transferring enchantments was the bandaid put over the only-getting-20%-value wound. If you take away the bandaid you leave the party without an otherwised assumed avenue of keeping up with the Jones'.
Weirdly enough, many parties don't have the ability to enchant magic items at all, so this argument falls flat. It's actually quite possible to have a fully functioning game of D&D that neither allows buying _or_ selling of magic items. It just requires giving out more magic items or balancing encounters appropriately.
4. One of the biggest things that makes 4e characters less versatile is the narrowness of the feat and power descriptions. If my dwarven fighter invested in lots of feats and powers that uses a +1 Hammer is handed a +6 Greatsword....its probably not in my best interest to use it.
Eh, +5 to hit and damage (greatsword) vs. +2 hit, +2 damage, maybe Con on miss. Greatsword totally wins.
But, yes, agreed once you tone down the example. Though I think that says more about the problems with many of the feats than with the items.
5. I suggest you instead hand out "Item Upgrades" instead of treasure parcels so that the dwarf with a +1 Magic Hammer can ease into a +2 Thundering Hammer and then a +3 Throwing Hammer as he progresses. Explain it as the same weapon he has used all along, it just performs better as he learn new tricks of the trade and hidden talents. If a character has a LVL 7 item and you hand him a LVL 12 item upgrade he could get the 20% value from his original weapon as cash on hand and pick out a LVL 12 item that suits his fancy. I even support the idea of being able to pick out a lower level item instead and get the difference in cash as well but some might disagree.
This is often a cool thing to do, and can even be quite thematic. Like 'As you chop off the red dragon's head, its blood running down your blade bursts into flame. Now it's a +2 Flaming' or whatever.
