No you would not harm the amplifier. You would simply increase the composite size (gauge), and decrease the composite resistance.
Speakers must be designed for providing multiple sections of the crossover to be separated. The main use is for bi-amping which is driving the different speaker drivers with separate amplifiers. Some people have used this to provide the same channel amplifier output to the different speaker drivers using wire separated at the speaker binding posts, and connected together at the amplifier - biwiring.
There is a theory behind this design, but the speakers definitely must be designed with a method of separating the crossover sections.
