Would people favour railways charging for luggage in the same way airlines do, and using the extra revenue to create space for it by removing seats or lengthening trains?
To get back on topic, should bicycles count as luggage for this purpose?
Introducing additional charges for luggage would just be another disincentive to use the train, people will then either drive or fly depending on distance.
Bikes are not luggage, they are more tricky to store safely, and need a different shape of space, if you know what I mean. If you had 1/3 carriage storage space on a 9 car unit you would loose may be 30 seats. However I am not sure how you would split it up for bulky stuff and bikes. Maybe side corridor with bike racks with bikes at 90 degrees, and some racking over the top for large luggage, and an open area for prams and buggies and anything too heavy for the over bike racks.
A bike reservation fee is OK, but does it apply to all services, even local ones? If I am going on a longer journey, where the off peak fare is say £100 retrun, I would be happy to pay £10 for my bike, so maybe £2 or 10% of off peak fare which ever is greater. However if I was paying £10 I would expect a guaranteed space, and some provision in the event of disruption, and I think this is where the problems come in, once you start charging, its the thin end of the wedge, charges will rise, and once you start charging its reasonable to expect a level of service provision, where as the current free system can be removed/changed/curtailed on a whim.