Is it permissible to perform Istikhara regarding changing a name that is impermissible according to Sharia, and in choosing a new name?

A name forbidden by Islamic law must be changed. There is no room for Istikhara (seeking guidance from Allah) in this matter, because Istikhara is for permissible matters, not for obligatory or forbidden ones. However, Istikhara is permissible when choosing among permissible names.