server-tools/field_validator/ir_model_field_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="view_model_fields_form_validator" model="ir.ui.view">
            <field name="model">ir.model.fields</field>
            <field name="inherit_id" ref="base.view_model_fields_form"></field>
            <field name="arch" type="xml">
                <field name="on_delete" position="after">
                    <field name="regex_validator" attrs="{'readonly': [('ttype','not in',['char','text'])]}"></field>
                </field>
            </field>
        </record>
    </data>
</openerp>