I would love the ability to increase ("decrease" isn't so necessary) the "full_load_sub_tasks" setting without stopping the task.
Stopping the task causes all currently loading tables to have to start over.
This becomes important when you are running multiple tasks at the same time (5 tasks @1 table, as opposed to the default 1x5), which is handy when loading a ton of tables overnight.
Then, as the quicker tasks wrap up, you want to give the extra bandwidth to a currently-running task.