The reason people say bathrooms aren't good is because of pipe holes really
A member on here's hamster got under the bath panel - under the bath panel are a lot of pipes and holes into the walls. She did manage to get him back out but there are plenty of hamsters who disappeared into walls and under floors and didn't come back.
I know what you mean - we had a hammy in a tiny cage about 25 years ago who lived to two years old, didn't have a good diet and seemed happy. But - he free roamed - we left his cage open. How he survived I don't know.
Since then a lot more research has been done into what makes them healthy and happy. A smaller cage isn't so bad if they have a lot - a real lot - of out of cage time.
Also what you don't hear about from the old days is hamsters crippled with arthritis because they didn't get enough exercise and other such things.
Ham-proofing a room is tricky. Some people are fine with balls - for a sensible person! Some people aren't sensible and hamsters get kicked in a ball or roll downstairs and get injured.
Putting something round the edge of the bed sounds like a good idea!