Why don't they deliver an initial report that builds on the original claims of China, Iran, and Russia. Outline the reports, affidavits, and court filings that further substantiate the assessment, and then follow up with the final version?
Also the EO says the DNI report is created in conjunction with other agencies and POTUS can receive direct and immediate updates without waiting for the official report. That says he can receive updates from MI and that MI can contribute to it.
They can rally to get it done since "We Have It All."