A little more background on your flights would be helpful. It seems to me that standing by for any flight after you have started an itinerary is not a problem, though an agent's help may be required.

For the record I once booked a redeye departing after midnight that had a connection to my final destination. With the help of a very nice agent I managed to standby for a direct flight leaving before midnight. That is not a situation I'd count on happening very often.