To make a bigger pad, please create it as a Copper shape desired and associtate it with the terminal.
Ok, that's no problem. Not sure why there would be a limit on the size.
Pads was developed with easy-to-use in mind. This tool will check values to see if it is practical and satisfy manufacturing process technology.
Padstack be outputed in gerber as a flash and shape as draw lines. There is no large optical aperture, so padstack size should be controlled
under a reasonable size.