There is a GRVW rating on your trailer if it is factory built. No matter what axles or springs you put under the trailer you by law can not exceed the rating. The manufacturer will not issue a new plate for that trailer and increase the trailer's load capacity. They have no way to know if the trailer has been altered or damaged.
That means if you get into an accident and the trailer weighs more then it is rated for, three bad things may happen. Your insurance claim will be denied and a citation for an overloaded trailer may be issued. And if there is a death or injury you may go to jail.
Load your trailer safely.