At a policy level I think you are screwed.
At a practical level, I suggest you don't book your flights until a day or two (use your judgement) before flying, therefore your corporate agent will not be able to get you X class and have to get a higher class of economy thus allowing you to bump yourself up. When flying regularly to FRA from LON I would always book the evening before the departure and the corporate agent could never get Econ tickets so they'd have to buy me first class.
The same techniqie can be used if your corporate agent is always booking you on, say, KLM and you want to fly with SIN. Simply inform the agent that you cannot get to the airport until 4pm (where KLM departure is 4.30pm and SIN is 5.30pm) thus meaning the agent has no choice but to book you out-of-policy on SIN. Obviously if there is a 6pm KLM you need to say that you need to arrive for a meeting at a time that the 6pm flight can't get you there.. Needs a we bit of research but pays dividends.