Allow me.
Passenger handling. Such a service at such a station could only be provided for through the already busy Stratford - Richmond / Willesden service. And realistically, most of the fans would want to head to Stratford. This concentrates the fans on to one route whereas what is required is to get them to Stratford where there are a further 2 tube lines, 2 DLR lines and 3 national rail routes with far greater capacity. Put another way, trying to get 60,000 people on to one platform for a 10 minute service of 5 cars is rather more difficult than getting 60,000 people on to 16 platforms with a train roughly every 30 seconds.
Feasibility. At Carpenters Road, it is currently three tracks. The track nearest the stadium (presumably where a platform could go) is only accessible from the GEML at Stratford (platforms 10 and 10a) or Bow Jn. There is no regular passenger service on that track, so one would have to be specially provided. Also the protecting signals for Lea Junction and Channlesea North Junction are in the way. So if a train towards Stratford stops there, it will block the junction in rear. Finally, there is Carpenters Road itself right alongside the tracks - remember this would be a busy station, so it will need wide platforms.
Timetabling. Adding in a stop on match days only would require a new timetable for each match. Now this isn't unusual - it is done for White Hart Lane (back OT). However it is unusual on this line, and would more than likely break junction working at one or more of Camden, Gospel oak, Willesden and possibly Clapham.
Cost. A station that only opens 30 times a year or so is still a station, you would still need full compliance to Disability regs etc. That means lifts or ramps. Even with 5 car platforms, you are looking at little change from £8m. And when would you build it? That line is only routinely closed for 8 hours on a Sunday morning, and 5 hours on Monday morning.
Even if it was feasible, and the timetable worked, and someone had the cash, then the passenger handling issue would kill it.