How can I add a popup from the Import Button in Odoo 13?

Question

I'm trying to add a popup form connected to a wizard when importing leads through the standard import funcionality. I've attmpted to override both the do() method in the base_import.import and override the load() method on crm.lead to trigger the same popup. I have included the load() version of the method below. Is there a way to do this or would I be best trying to add an option under "Map your columns to import" or just create a config option and skip modifying the import function all together.

    @api.model
    def load(self, fields, data):
        if not ('assignment_selected' in self.env.context and self.env.context['assignment_selected']):
            import_vals = {
                'fields': fields,
                'data': data,
            }
            view_id = self.env.ref('mdlu_lead_assignment_ext.view_crm_import_wizard').id
            return {
                'name': _('Lead Import Assignment Options'),
                'type': 'ir.actions.act_window',
                'res_model': 'crm.import.wizard',
                'view_mode': 'form',
                'views': [(view_id, 'form')],
                'target': 'new',
                'context': dict(self.env.context, import_vals=import_vals),
            }
        recs = super(Team, self).load(fields, data)
        return rec