At the very least I hope fixed placement of items is easier. That way they'll serve the same purpose they served for me in Morrowind: a vulgar display of wealth.
They should definitely be consumable as alchemical ingredients. Plus I find it amusing that my character may amass so many gems that he actually considers eating them as a valid form of use.
On the more controversial side, it would be really interesting if regular coins had weight. What does that have to do with gems? Well, why carry around 100 coins weighing over a pound when I can carry one gem that's less than a pound and is worth more than 100 coins. If money had weight, then all other loot (especially gems) instantly becomes more valuable simply for its ability to concentrate wealth. Furthermore, mercantile becomes an even more valuable skill as it allows you to realize a greater percentage of the gem's actual value, when using it as a proxy for coins.
This.
I always found it silly that you could carry fort knox around with you, but not a grocery store. If gold had a reasonable weight of 1 or 0.5, it would suddenly make gems MUCH more useful. Sure, you would lose a bit buying and selling, based on your mercantile skill (if that still exists?), but it would make carrying large sums much easier - or even possible.
Daggerfall actually allowed you to trade in gold for letters of credit, which I always thought was kind of nifty as well - though I'm not sure how that would work out in the wilds of Skyrim.