On Action for Required Select CCK field "None" shows up as a Choice

I had the same problem, and I tracked this behaviour down to line 74 in fields.action.inc: $field['required'] = FALSE;

I think this is very intentional, though – when looking at more of the code I conclude that it is also used for multiple-value fields, including the ability to only add new values (and not replace the existing ones). If the fields were required, you would always have to set a new value to all the processed nodes – while leaving it empty allows not affecting (required) multiple-value fields.

There are three possibilities to solve this, as far as I can see:

1) Keeping the current code and taking care of Shai's and my problem by a form_alter. This is good if I'm having the edge case.
2) Change the code to respect required fields, and forcing those who want to use multiple-value fields in the way described above to do form_alters. This is good if they're having the edgiest use case.
3) Change the code to check whether the field is a required multiple-value field, and only then unset the required condition.

I'll make some experiments and return with the results.

I went along track 3 above. Attached is a simple patch that moves the required=FALSE to only multiple-value fields.
Note that this patch will force the user to set fields even fields that will not be used on the update (which may be the case if you're updating many fields at once). This is a feature, not a bug. ;-)

...patch now with --no-prefix to make it easier to apply with the -p0 option. Also rerolling patch against dev.

Assigning to infojunkie for review.

The fact that

this patch will force the user to set fields even fields that will not be used on the update (which may be the case if you're updating many fields at once)

make the UI counter-intuitive. A better solution is needed.