I think you can not change your ID.
If you change e-mail,It may be that you change your ID.
NO we can not just change id.
You can abandon your id and make new one, but you must export and import everything (
hatena point, blog etc) by yourself. Letters you abandaned will never reused.
You can use sub-account adding to your main id. That is very similar to changing id, and there is no need to export and import hatena point.
Hi, Ninja Unicorn
Why you want to change your id?
You could add a new sub-account to your account.
You can succeed to without losing your property by using your new subaccount.
You could create your sub-accounts by 追加 button on the following page: