Importing users that will be installed by programs

Solution 1:

No, it will not cause problems.

Creating users from random software is done with a check where is tested if the user already exists.

And there is a better method for creating users. The command newusers {file} where {file} is in the format

loginname:password:uid:gid:comment:home_dir:shell

(and yes, that is the password file format) will create all the users in that file where existing users are skipped. It will also create the home directories (where yours will not).

See the newusers manpage for some tips and tricks (the password field is something to have a look at though since it wants plain text and not encrypted passwords).