Hmm, 'keep bonuses in the right ballpark', maybe - I hear a lot about "feat taxes" and stuff, but I'm far from convinced that exact bonuses are all that critical. Magic items allow some variety, here - take the extra plus, or get some interesting properties/powers. That said, the 'Inherent Bonuses' takes care of the 'ballpark bonus' need; I wonder whether this will leave too much scope for other attributes of items, but you can always give less items, as you intend, so it's hardly insoluble.
I've never seen a need for the feat taxes like Expertise. As far as items go, though, I think those are a bit more relevant, though probably not significantly noticeable until you are getting into Paragon.
Either way, outside of that, I can't think of any magic item properties or powers that a party would ever actually 'need' - and while the lack would be a reduction in power, I think it is mainly in focused power. Over the course of the day, the magic item party isn't too overwhelmingly ahead of the non magic item party. However, in any given short term scenario, they can probably bring a bit more to bear.
But I think that will honestly make it
easier to plot out and design encounters, since the party's capabilities will be much easier to predict overall.
OK, I can see how taking gold pieces out of the 'game' part altogether and having it buy fluff could be a useful function. D&D does need some "measure of character success" that is not linked to adding in-game power, and this is one way to do it. If some of those elements become useful on adventure, though, you might get a warped market (since it will be "obviously better" to players who are 'playing the game' to buy attributes that give adventuring bonuses)
Sure, but that's why magic items are out of the equation. That doesn't mean they won't have options that aren't
usable in combat, but those options won't necessarily be potent enough to be worth giving up a chance to buy their own boat. And they will probably be more likely to have consequences than magic items would.
So the player who is all about combat effectiveness can hire some mercenaries to protect him in combat - and they will provide some bonuses, but also be quite likely to get killed if he uses them too aggressively, and consequences can easily develop from that.