So here's the situation:

I've overridden the Single Page Register including the controller because I've made some changements to the registration process. So far so good. Everything works.

Now the goal is to show the registration form/page in a modal on a normal Page.

Is that possible?

If I kind of reproduce the form in my modal, do some changements in the do_register method of the controller to receive the validation error messages it works (kind of).

But I hate to copy code.