I'm more in agreement with b) than with a)
I'm fully on board with encouraging it and having a dedicated cargo space SO LONG AS I have to pay for it properly.
It's one thing I like about amtrak's policy: if you have a normal bike, that's a fee. if you have a folding bike that fits in the same volume as luggage: you can use it as a carry-on, for free, _instead of luggage_.
It means that you're encouraging usage of portable bikes on mass transit over bulky ones, giving a reasonable option, and requiring that said reasonable option be paid for by the people utilizing it, not everyone else
I find this quite reasonable overall