I've been pointing out a distinction between:

A. Interstate arbitration or negotiation over trade disputes, tariffs, foreign investment, and so on

B. A corporation (i.e. "investor") contesting the domestic legal practices or standards of a state in a non-state (i.e. international) venue.

It's really quite simple. If State A wants State B to change their laws such that investors from State A or corporations affiliated with State A can competitively enter State B's market, then that is a state-state issue. Same thing for border traffic and control, standards for quality, measurement, reporting, etc.

Crucially for our discussion, if Corporation A wants to claim that State B is violating its own laws or the conventions of a trade agreement/organization to which State B is party/signatory, then a specialized international court does indeed make sense.

However, if Corporation A wants State B to change its laws in such a way as to benefit Corporation A, then there should never be any judicial recourse, in any venue. In case you have forgotten, corporations already have the capacity to create political lobbies advocating for that very goal, and that should be sufficient.