The command-line interface you propose is perfectly fine as long as it's documented.
The GNU coding standards recommend providing long options. It is easy to have those in addition to the short options with Getopt::Long::Descriptive.
--inc=n
+n
to increase the current service by n
--dec=n
-n
to decrease the existing services by n
--abs=n
n
to create n number of services (irrespective of the number of existing services)
--no-op
no change in operation, existing services continue as is