Why or how is "If we meet when I come to Paris, ..." wrong as a clause?

As a clause, it looks fine to me.

For me, a subjunctive would seem natural as the completion. Such as "If we meet when I come to Paris, perhaps you could show me your city."

There are lots of ways to frame this.

If we should meet when I'm in Paris next year, you could show me your favourite places.

Or as a question "If we should meet when I'm in Paris next year, would you show me your favourite places?" or 'some of the sights' etc.