Well, the first question is whether the permission should be fixed rather than the removing the accessibility. Of course, it is probably too dangerous having a system that allows modules access to any private field. Perhaps we need to split out two versions, one that makes methods accessible and the other that returns null if it isn't accessible.

Secondly, you haven't added setAccessible() anywhere else to make up for removing it, so this change should be breaking world serialization and network serialization anywhere there are private getters and setters.

Thirdly, I'm uncertain whether getters and setters should be used if they are private, rather than defaulting back to directly modifying the field. Thoughts?

Fourthly, the reason I suggest returning null if the method isn't accessible is because it won't be usable as a result, so you'll get an error down the line - if you use BindHelper.bindBeanProperty on a property with a private getter or setter.  Better to pretend it doesn't exist.