I think the OP question indicates a much wider problem with cycles on trains, as the current situation is unworkable in a lot of areas. TOCs requiring reservations is fine but that rules out the commuter/traveller who may need a flexible journey. Provision on busy trains is barely adequate and may be limited by time on some routes. RRBs are a problem. Folding bikes go some way but are not suitable for everyone. I had a bad experience with one a few years ago where the frame failed, despositing me on the ground in a heap, cuts and bruises resulting. I was at the top end of the weight limit, for larger rider they are not suitable.
I think that this is one area where it needs intervention if we are to keep the current TOC based method of service delivery, to set out a common set of rules across the system, so that as a minimum its easy work out what is possible.
RRBs are also an easy way out for a lot of operators, in some cases there are diversionary routes, but because of route knowledge these cannot be used. Perhaps if there was a substantial penalty for TOCs using RRBs where diversionary routes exist there would be less reliance on them. One thought would be to use the trailer idea as used by the airport buses in London in earlier years, TOCs or whoever purchase the trailers, relativley low outlay, and contracted companies have to provide standardised (across network) towing hardware. Buses/Coaches then perform their normal duties without trailer, and when pressed into RRB duty collect a trailer for bulky luggage and bikes. Probably too joined up for the current railways. A coach can store 4 full size bikes in the luggage area under the body but that doesnt leave much room for other luggage (used to travel on a private company provided coach service between two locations, and people would take their bikes to give them some mobility at the other end, it was part of what made it work instead of going by car)
Rail travel and cycling to and from stations at either end of journey should be a good way of travelling, reducing car usage. Cycling is good for the 1-5 mile jouneys where walking would take too long. As for a charge to carry a bike, thats fine as long as service provision is adequate, but realistically given the current design of rolling stock that is not going to happen, many trains do not even have adequate luggage storage. Without going to far off topic I think it is part of the 'How should the railways deliver their service' discussion. Are they a public service in a true sense whose purpose is to allow other parts of the economy to function better. I dont think carrying cycles is ever going to be profitable for a TOC, hence the current squeeze in terms of pre booking etc. So it really is going to be up to governments to set a direction on this, but I dont think that will happen.
I think what will happen is that bikes will be squeezed off trains, a death of a 1000 cuts, reservation requirements, lack of capacity, time of day restrictions, RRBs... Not the right answer, but its the way its heading.