I'm not entirely sure I understand your question, so please let me know if this is off target:

According to the Heat API reference, to create a new stack you POST to /v1/{tenant_id}/stacks. This POST request can include an environment parameter, which "provides a JSON environment for the stack".

This seems almost exactly like what you are asking about in the subject of this question.

The files parameter is for passing in provider templates; it maps filenames to JSON template content.

If you have remote access to the HEAT API, it seems as if you could also install the Heat command-line client (which talks to a remote Heat server using the API), and then create stacks via the heat stack-create command.

The Heat client also provides a good example of how to interact with the remote API.