Post: #4

I don't think this would impact the server performance in any way
Take the time that Sphere would use to write a 1kb string to the disk then multiply it by 1000 players, maybe 0.1 or 0.2 second increase in the save time? RunUO does not have anything similar like tags, so each item type has its own "binary save format" and every custom item may also be saved in its "own format" and there is no performance issue that can be related to the save diversity
Gumps also does not impact on the network performance, Vorspire from RUO developed a system called Super Gumps that updates itself about 10 to 20 times itself on the client screen with no performance issues (A gump progress bar that is updated really fast to show the spell cast time can be used as example)
I don't know how sphere deal with gumps, but since this spell bar does not need a fast update, there would be no performance issues related to it
Optimization is always welcome, but you will be fighting for performance against memory/disk usage

I would not fear using this system in a live server, unless I had a very limited hardware; I would just test it before it goes live, like anything else