What I got
I have a directive like this one:
@Directive({
    selector: '[appValidateOnSubmit]'
})
export class ValidateOnSubmitDirective {
    @Input('appValidateOnSubmit')
    set appValidateOnSubmit(form: NgForm) {
        // do something with the form
    }
}
Usage:
<form (ngSubmit)="submit()" [appValidateOnSubmit]="myForm" #myForm="ngForm">
    <!-- ... -->
</form>
This so far works perfectly fine.
Question
Can I somehow eliminate the template reference variable myForm from the HTML? So that I can write simply <form (ngSubmit)="submit()" appValidateOnSubmit> instead of the much longer <form (ngSubmit)="submit()"[appValidateOnSubmit]="myForm" #myForm="ngForm">?
Background is my answer here which I am trying to improve.