A guide for professional photographers. My advice. If you want to include moving trains or track in your portfolios or shoots, learn how to do it safely. Contact the local railfan groups through the NRHS and see if fan trips where photography is expected are coming up. Talk to the people at the local railroad museum. Make an investment in doing it right and keeping it safe.
Honestly, you can live without flash in daylight. More than one camera is just ridiculous unless you are shooting both still and video in different cameras. And DX Nikons saves you weight over FX. For a shoot like this I would probably just use a fixed 35mm lens and set up shots by moving back and forth. Or use and 18-55 for zoom.