If you did that, the Black Ajah would pop up to snuff you out. Wasn't that the whole reason Cadsuane had gone into retirement, more or less?
Anyway, with regards to portable gateways, didn't the Shaido have some boxes given by one of the Forsaken, which could create gateways? Or was the entire premise there that said Forsaken was actually creating those gateways, and the boxes no longer worked when he (?) wasn't around? I am struggling with remembering the details, but they did for sure stop working once the Shaido were spread to the different corners of Randland...