Hi,

in the first view you can keep the field as editable then inherit the same view and assign a group to this view and in this inherited view, set the field as read-only, so for use belonging to this group the field will be read-only and for other it will editable.

<record id="view_partner_property_form" model="ir.ui.view">
        <field name="name">res.partner.purchase.property.form.inherit</field>
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_partner_form"/>
        <field name="priority">36</field>
        <field name="groups_id" eval="[(4, ref('base.group_multi_currency'))]"/>
        <field name="arch" type="xml">
            <group name="purchase" position="inside">
                <field name="property_purchase_currency_id" options="{'no_create': True, 'no_open': True}"/>
            </group>
        </field>
</record>

Thanks