Redmine

So using Reposman.rb should create Repository even if SCM Module is enabled on project

I don't understand your problem.

I've just tested this in redmine :

Create a main project with SCM module disable
Create a sub project 1 with SCM module enabled
Create a sub project 2 with SCM module disable

And reposman say :

% ./extra/svn/reposman.rb -s /var/git -r localhost:3000 -o www-data --test           
running in test mode
    create repository /var/git/subproject1

So, if SCM module is enabled in a subproject reposman create a repository.