I cannot image wanting to haul a trailer when traveling by trains. Especially with jumping on and off trains as in your plan. If that line accepts RORO then your trailer will still need to be boxed. If it does not offer RORO then both trailer and bike will need to be boxed. A major PTA.

My advice is try and get yourself down to two panniers. Then you can carry them on. You might even consider leaving the camping gear at home, bite the bullet and pay for motel or try to find warmshowers or couch surfing hosts. Carry the bags on.

You could also get yourself a large duffel and stash the bags in that to make it easier to carry on.