Dynamic (Post) Stack Sizes
I would like to see a system that is less ridged about stack sizes (i.e. stacks that change with the amount in your possession. Two quick ways to approach this would be, percentage of overall owned, and by market value.
The first would be straight forward. Give a % and TSM posts at or above that level. At 5%, 200 would post as stacks of 10 and anything below 20 would would post as stacks of 1.
The second would be more complicated, but better in my opinion. Give a (changeable) list of gold values that determine stack size in tiers. For instance:
100G+ Value - Post as stacks of 1
50-99G Value - Post as stacks of 5
10-49G Value - Post as stacks of 20
Under 10G Value - Post as stacks of 50
This would allow better manipulation of stacks according you your needs without changing them in groups all the time. I am aware multiple operations can be set up, but that system only allows for degrading stacks to be posted.