I think the smartest thing to do would make upkeep more time based as well. The goal of upkeep is to keep people from wearing expensive armor all the time, right? Well, there's the obvious failure to achieve that objective. So what if you made it to where you could only use an item so many times per time period? Let's say every time your character dies, it loses a Black Armor because that's the armor your wear. Now let's say you gain a Black Armor every 30 minutes. Over a day you would gain 48 Black Armors and if you just used up every Black Armor you have each day, you would be able to die 48 times in Black Armor before you had to switch to something else. But in contrast, you would be able to get a cheaper armor like Tunic over Mail at a much faster rate so you wouldn't run out of it so quickly. This kind of thinking should be able to keep people out of plate all day long if implemented correctly.
Of course, if this was done individually for every piece of armor in your inventory, you could just buy all the heavy armor and still have enough to go in plate all day long. Therefore, for every item class, you should be able to show what percentage of your efforts you want to put in each item. So if for armor, you put 50% into Black Armor at say 30 minutes per item and 50% into Tunic over Mail at say 10 minutes per item, after 24 hours, you would have 24 Black Armors and 72 Tunics over Mail.
However, I wouldn't suggest removing all gold based upkeep as that would screw with the market by dropping the value of gold. Instead, I would say the rate at which you make items could increase of you invested more money into it. So where you would choose which items to add up to get 100% of your effort for armor, you could do so at say 100 gold per day. Or you could go up to 200% if you're willing to pay 10,000 gold per day. And maybe 300% if you're willing to pay 50,000 gold per day.
I feel like I'm missing something, but this all makes sense in my head. It would however require adding a few columns to a table or two, more forms to the equipment layout page, and some coding that maybe only I am awesome enough to do.
