Excel or Google Sheets Macro to change format - TSV files to CSV

We need someone with Google or Excel Macro experience or similar to create a solution which converts all files within a folder from a TSV format to a CSV format. Also it needs to change the content and perform certain operations on some fields as described below:
- add a number of columns
- Vlookup to an external file to pre-fill 1 column
- duplicate certain header values across all rows and remove heater values
- ability to pre-select certain values to be prefilled prior to the macro being run

Exact specification of the transformations for each column are provided in the samples attached.
1. Original TSV file - AAABBBCCC123 - this file shows the original file format. We would have multiple files per folder.
2. Final CSV file.csv - this shows the final CSV file format. We can have one final CSV file which uses the same heaters at the original TSV files or we can have the same number of CSV files generated as the original number of TSV files.

This preparation is necessary so the files need to be upload into a different system which is expecting the format shown.

Thanks