When we first started discussing this in the other thread, I immediately began thinking along the lines of 5E's Downtime Activities and its 4E trial balloon, the Dragon 424 article "Achievements" by Robert Schwalb. Therein he breaks Achievements down to four categories: Association, Influence, Information, and Material. But the system isn't developed as fully as it could be, nor is it divorced from the treasure rewards system (which, as most of us seem to agree, is really just a subset of combat character mechanics--or choices between combat utility and resources spent that take away from that ability, a pernicious divide if ever there was one!).
My initial concept is that, by divorcing the traditional rewards economy (i.e. magic items and combat utility) from a separate monetary economy that contributes to the kind of social "pillar" reward that Schwalb presents, things become much more interesting as characters build and make choices within both of these pillars.
For example, as it stands right now, the group that ventures into the Dungeon of the Fire Opal and retrieves that fist sized ruby from the statue of the efreet has little option but to sell it to buy magic items to advance their characters according to expected development. But that seems a waste of a potential plot item. Couldn't that item serve as a locus of intrigue and influence in the gameworld, and outside of DM fiat? (I mean, it's always easy enough for the DM to have assassins from an ancient fire cult come after the jewel, etc., but I'm talking about player empowerment in world building, in the same way that making background choices, feat choices, magic item choices, etc. can drive the narrative.)
Might not those who carry the jewel achieve influence in the Crimson Court of the tiefling duke by fashioning it as the centerpiece of a crown, for instance, or use it to create a permanent portal to the City of Brass, etc.? Wouldn't it be great to track the wealth of characters as they advance in level according to such a parallel rewards system to drive gameplay in other ways beyond simply as units to be instantly exchanged for the best magic items?
Sure, this is good. The necessary and difficult concomitant to all this is you have to plausibly divorce the magic item 'economy' from the gold piece economy. This isn't super easy to do in a non-forced manner. I mean, lets face it, if someone needs food bad enough they're going to trade their +1 sword for some cash so they can buy rations. This is particularly true with a 'commodity' magic item like a +1 sword. Even if such an item is quite rare its still simply a small increment of power better than an ordinary sword, so its relatively straightforward to equate it to existing items and prices, and there's likely to be plenty of willing buyers (anyone that uses a sword, given the right price).
So, one thing that you would want to avoid is such simple commodity magic items. Or if they exist then they're a class of things that DOES cross over between gold and magic. To some extent that might not be a terrible thing, you COULD sell your +1 sword, or buy an extra one if you happen to get a LOT of loot. If its not a really critical thing to have though, it won't matter too much. So either these types of items could be very common and thus basically just ordinary items (albeit maybe significantly more expensive than mundane swords), or they could simply be incredibly rare ancient items that are almost never found and thus not something you can plausibly find for sale.
High end items aren't so much of a problem. The fire opal for instance is unique in all the worlds. Moreover whomever owns it has a big target painted on them. You probably COULD sell/trade it, at far below par, but buying such a thing is beyond impossible, and at best would represent an adventure all of its own on a par with looting it in the first place.
There might still be a problematic middle ground of items though. Imagine a 'ring of spell storing', it could be quite valuable, but in the right situation someone might sell it to you. Its probably not unique in most settings, though it could be quite rare. Again, you can make these things super rare, so they just aren't ever for sale, but you probably can't make them commodities, unless you're aiming for a very magic-heavy world (plus even if they are commodities their high utility means buying them is likely not optional for an adventurer).
Note that the same considerations now apply to creating items. I'm reminded of the 2e rules, which basically rule magic item creation to be impossible (you can do it, but it really isn't worth it 99% of the time). Clearly you would want to avoid 4e's Enchant Item concept.
Actually the current item rarity isn't so bad. If you assume that the items anyone can enchant (common items) are basically commodities and maybe even lower their costs so everyone just makes some, then the rare items are left as pure treasure awards, with enchanting them being only a plot device.
