It should be possible to convert a form made in the legacy editor to the new editor, so you avoid the hassle of creating a new one and switching out all the places it's used.
Absolutely, great idea! Not being able to convert legacy forms to the new editor is a big issue right now because some functionalities of the new form editor are not available in the legacy forms. As an example, we have put restrictions (number of caracters, numbers only) on a text type property that is already being used in multiple legacy forms (more than 70), those restrictions apply to the new form editor, but not to the legacy forms, meaning that those legacy forms enable to put incorrect data (that doesn't respect the property restrictions) in our CRM.