I want to create selection drop down from the data from a model. I can't use the many2one relation because the value from the selection shouldn't be only values of id, but normally they are string codes.

My model for the selections

class Selections(models.Model):
    _name = 'hr.selections'

    name = fields.Char(string='Name', required=True)
    usage = fields.Char(string='Description')
    in_use = fields.Boolean(string='Active', default=True)

    fields_ids = fields.One2many('hr.selections.fields', 'selection_id')

    @api.model
    def get_selection_field(self, selection_name):
        selection = self.search([('name', '=', selection_name), ('in_use', '=', True)])
        selection_list = list()
        for data in selection.fields_ids:
            if data.in_use:
                selection_list.append((data.value, data.name))

        return selection_list

class SelectionsFields(models.Model):
    _name = 'hr.selections.fields'
    _order = 'value asc'

    name = fields.Char(string='Option', required=True)
    value = fields.Char(string='Value', required=True)
    in_use = fields.Boolean(string='Active', default=True)

    selection_id = fields.Many2one('hr.selections', ondelele='cascade', index=True)

And I use it in other models like

class Something(models.Model):
    _name = 'someting'

    selection_field = fields.Selection(lambda self: self._get_selection('selection_name'))

	def _get_selection(self, selections_name):
		selections_list = self.env['hr.selections'].get_selection_field(selections_name)
		return selections_list	

It gets the data and shows the selection options, but if you add a new record to SelectionsFields, you have to upgrade the module before it's shown. Is there a way to do this without module upgrade every time? 

And NO I can't use many2one list widget for this, because its should be an addon module that doesn't change the whole program.