I suggest faking it.
Use a text box that looks like the maximize icon.
Create an action that sets a variable.
If the variable is set, show a large chart with the pivot table fully expanded.
Use a text box that looks like the restore icon.
Create an action that resets the variable.
If the variable is reset, show the restored pivot table with the fields collapsed.
You couldn't change the font-size or the column-widths by maximizing an object. You could go with the suggestion from mwoolf and creating several specialized objects which you could show/hide per buttons and variables.
Otherwise adjusting the zoom-level of the application will be probably the only way to get your object bigger (within the AJAX client just using ctrl + scrolling from the mouse like in each other web-site is quite practically for it).