Can MailStream Plus combine/consolidate Mail.dat files from several mailings into one?

Product affected: MailStream Plus™, all versions, all platforms
No, MailStream Plus™ cannot do that.  It can only generate the Mail.dat file set for the mailing that is being done at the time.  It has no option to combine the file set with Mail.dat files from other mailings.  

It was suggested to the customer that they consider looking into using a 3rd-party Mail.dat editor application.
UPDATED:  May 16, 2019