Cages is definitely a hard one, especially if you have more than one hog. I think it's maybe because I'm used to traveling that I was prepared in that aspect. I take my hedgehogs everywhere that I go if I'm ever going to be gone for an overnight or longer. They literally are my kids and I don't trust anyone with them. However someone who isn't used to traveling with their boys may have some issues with this. If you only have one you can use the bathtub as a temporary solution but I use pop up playpens made for dogs. That is one thing I would definitely suggest for others.
Something that I was not prepared for was their wheels, I did have to leave them behind. I do have mounted wheels and I wasn't able to take them with me. This isn't a huge deal for overnight or other short trips, but I really hate not having them being able to run. Their cages (especially the pop ups) are a little on the smaller side (just over 5 sq ft) so that's something I feel like I should figure out.
Honestly, though, I think the fact that I frequently travel and have my hedgies out with me that I was more prepared. I probably take my hogs out and about with me about once a week to the park or around the town so I've learned over time what the need. If you do travel a lot, I would get live animal stickers for your (hard sided) pet carriers. If anything should happen when out and about, I want it to be easy to recognize so that my hogs can be rescued as well. Similarly I'm thinking of making a door plaque for my apartment that alerts people that hedgehogs are in the residendce so that if there's ever an emergency, and I am unavailable, someone will know to get them out.