So I'll answer myself, hoping that might help other people.

Having several views of the same type is very recurrent in openerp, so the most complete solution is not the priority, and it's not the "by action" method, it's the DISPLAY MODE solution.

So for example, for an action action_orders, I'll assign for each DISPLAY MODE ( the horizantal list of possible views to display that we have below the search filter ), the view to show, because I have of course many possibilities for each type of view. and that is possible by this code : 

        <record model="ir.actions.act_window.view" id="action_sale_order_tree">

            <field name="sequence" eval="1"/>

            <field name="view_mode">tree</field>

            <field name="view_id" ref="view_order_tree"/>

            <field name="act_window_id" ref="action_orders"/>

        </record>

        <record model="ir.actions.act_window.view" id="action_sale_order_form">

            <field name="sequence" eval="3"/>

            <field name="view_mode">form</field>

            <field name="view_id" ref="view_order_form"/>

            <field name="act_window_id" ref="action_orders"/>

        </record>

So I assigned via the view_id field, the id of the view to display when clicking on the display mode, according to what type of view I want to display. all of that is hapenning when action_orders is invoked via menu click.

So I hope that helps someone.