factory_reference_invoice/views/account_invoice.xml

<?xml version="1.0"?>
<openerp>
    <data>
        <record id="account_invoice_form_view" model="ir.ui.view">
            <field name="name">account.invoice.form</field>
            <field name="model">account.invoice</field>
            <field name="inherit_id" ref="account.invoice_form"/>
            <field name="arch" type="xml">
                <xpath expr="//tree/field[@name='product_id']" position="after">
                    <field name="product_factory_ref"/>
                </xpath>
                <xpath expr="//field[@name='invoice_line']/tree//field[@name='account_id']" position="attributes">
                    <attribute name="invisible">0</attribute>
                </xpath>   
            </field>
        </record>
        <record id="account_invoice_supplier_form_view" model="ir.ui.view">
            <field name="name">account.invoice.supplier.form</field>
            <field name="model">account.invoice</field>
            <field name="inherit_id" ref="account.invoice_supplier_form"/>
            <field name="arch" type="xml">
                <xpath expr="//tree/field[@name='product_id']" position="after">
                    <field name="product_factory_ref"/>
                </xpath>
            </field>
        </record>
    </data>
</openerp>