Build Custom entity or Use Drupal content types?

Hi all,

I am working on a project which will be a content repository for an organisation and they will be fetching the content from Drupal using web services. There are numerous types of contents in the website with numerous fields.

One content type have nearly 18 fields in which most of them are fields collections with number of values set to unlimited.

We are thinking of using custom built entities for the content types that will be used in the project to have a lighter footprint and reduce the number of tables in the database.

What are the possible complexities that I can face using the method? Or is it fine to use Drupal content types for this?

FYI we also need functionality like revision, metatags fields, etc with the entity.

Thanks.