Well, what you describe should be relatively easy with Toolset, even without the new release of the Many To Many features in Types.
This coming release will make one thing in your above project easier:
The handling of many-to-many relations, as your Players have in Teams.
Right now, for this, you need to create an intermediate Post Type so to connect each player and team multiple times.
In the future, this will not be required anymore, and you can just connect many players to many teams with one workflow.
The other relations, as you describe them, are just a parent/child chain, which is doable with Types / Toolset.
I would even suggest thinking about Taxonomies or Fields, instead of Post Types, especially for your Sports.
It seems redundant to me, using Post Types for this.
The rule of thumb I follow when building such complex structures is to classify the data as follows, on top the one to use the less, bottom the one to use the most:
- post types
- taxonomies
- fields
This means I always try to have as fewer post types as possible, and enrich them with Fields and taxonomies, instead of building complex relationships and query them, I can just run one query and filter posts by directly associated meta-data or taxonomy terms.
Anyway, with the current Types, your goal is achievable, and it will be easier with the new Types release.
Toolset can also create, edit, login/logout users.
It can also add User Fields, which act more or less the same as Post Fields.
We provide ShortCodes for Custom Log In, Log Out, forgot password and more forms.
With some custom code, you can even let the User Data "talk" to the post Data on particular CRED form Submits.
Please open a new ticket for this topic if you require more help on it, as it is another part of Toolset, not related to the Post Types creation.
Please let me know if I can help you further!