You can edit the class, and uncheck the "required"-checkbox, if the problem is that eZ doesn't allow you to leave fields empty.
But if you want to, for example, make eZ accept values in the email-datatype that doesn't qualify as an email-address, you will probably have to make a new datatype as an extension.
When publishing content, ez doesn't allow a lots of tags, so the editors get tens of lines on top with messages (input did not validate..tag removed...).
I want the system to still validate, but not give the messages. There have to be an easy solution to turn this off``??
<i> ez doesn't allow a lots of tags, so the editors get tens of lines on top with messages</i>
This depends of field which you using, you can switch from xml filed to text field, then you can use all xhtml tags, but this is of course not a way how to manage with content, xml filed accept couple of tags, because we want to separate content from design.
You can edit file edit_validation.tpl for admin design. Look in to design\admin\templates\content\edit.tpl there is {include uri='design:content/edit_validation.tpl'} which returns validation output and edit_validation.tpl in the same directory.