If I've lost access to my Apple ID, are there downsides to creating a new ID?
Have you read the Apple FAQ about Apple ID here?

There is various information on how to retrieve access to an ID, could be a good place to start rather than abandoning the ID as previous purchases will be linked to that ID.

As covered in the FAQ, since you have never been able to merge Apple ID - it's probably worth the effort to contact Apple to get the original account unlocked / password reset.

Q: I have multiple Apple IDs. Is there a way for me to merge them into a single Apple ID?


  Apple IDs cannot be merged. You should use your preferred Apple ID from now on, but you can still access your purchased items such as music, movies, or software using your other Apple IDs.