As far as I can tell, a corporation is already not treated as a literal person, only it has some of the same rights. Simplest example, a corporation can't run for a public office. What do you suggest should be changed, no 1A for a corporation?

Yes, corporations are not people, and do not get rights, period. They're legal fictions that get privileges that we the people grant them.

If you want to represent yourself commercially as a person, your rights as a person can be extended to that legal fiction.

If you want legal fiction that you can dump when it's convenient and isn't tied to you as a person, then that legal fiction gets no rights and only certain privileges.