Hello @Daniele
It would be great for Pro Forms to have an advanced option to validate fields client side with custom RegEx that you have defined.
So that when a user enters a wrong value to show him a message and the Pro Form can not be sumbited.
For example, you define a Name and Surname Field and you add a RegEx validation of
^[a-zA-Z]+$
That way the user can not add numbers or symbols to Name and Surname fields and a message just like the image below should appear: