[TYPO3-mvc] best practice for multiple form validation

[Domi]

Hello,
I was reading quite a lot of posts but couldn't find a good answer for 
my problem, often the posts were bit older so maybe there is another 
solution out.

I am writing a little extbase feuser registration and filled all 
@validation values into my model.

But now there are some required fields, which are not used in all of my 
forms, but the validation throw false, although the values are not 
displayed inside of the form.

Is there an elegant way to ship around, without to write for each form a 
custom validator? Is it possible, that the validator only validates 
values, which are present in the form?

Thanks for any help,

Dominic