Correlation between my own ideas and others.
Have a slash command /inv. You put the number of the row after /inv. /inv 1 is weapons. /inv 2 is tools, and /inv 3 three and on can be different types of resources like wood, ore, and so one.
This would limit how much of each type you can have, and that is realistic...
There is also another option, increasing the number of items a person can carry. I've seen this on one server, but when I hit Q to drop down my inventory, it had about 15 spaces instead of 5. This would be a simple solution, but inventory would still be limited (and I think it should to an extent be)