Each project within a suite can have it's own NameMapping file. However, any applications that you need to interact with within that project are mapped within that singular file. So, no, you cannot have multiple name mappings files per project.
Actually we were the team of 4 working on the same project but with 4 different tested apps. Whenever we try to merge our code in git we are getting merge conflicts. Resolving merge conflicts on testscripts is not a tedious one but resolving conflicts on 'Namemapping' file was a real headache. However having separate namemapping file for each app can atleast ease our job and less chances of getting merge conflicts.