I've extend crm.lead object in a custom module but since I've do this I have no statusbar in form view but only the current state indeed. See picture:

and source code:

class crm_lead(osv.osv):
    """ CRM Lead Case Juliana"""
    _name = "crm.lead"
    _description = "Lead/Opportunity"
    _inherit = ['mail.thread', 'ir.needaction_mixin','crm.lead']
    _columns = {
        'planned_revenue_month': fields.float('Revenus mensuel attendus', track_visibility='always')
    }