File Write for Header, Line and Total Levels

We are working on a project where we need to write a file and send to an external entity. As a part of this file write, we need the following

A Header level (basic info)

A Line 1 level (with specific data requirements)

A Line 2 level (with specific data requirements)

A Trailer file (includes Line 1 level record count, Line 1 level record count, and total count for Line 1 and Line 2 records)

How can we write data to a file with these different levels that have different specific data requirements - WITHOUT using File Layout (since lines have different data requirements)?

- Line 1 will have payment info for each supplier