Is there a chance to read 'it' in '1' as introductory it?
No, Ahmad. "it" cannot introduce a subject in extraposition in that sentence because it would be ungrammatical and nonsensical to say:
* That the report is baseless is to submit.
Instead, the passive voice is grammatical and meaningful, as David told you:
- That the report is baseless is (hereby) submitted.
If that is not so, then kindly explain with an example what you mean by "It could be used to answer the question "What is it for?", where "it" refers to something established in the context."
I imagine that (1) could be a possible answer to this question:
A- What is the purpose of your letter to the manager?
B- It (The purpose of my letter) is to submit that the report (written by my supervisor) is baseless.