Description of problem:
When user wants to re-define anything in a unit file, he's supposed to create a new unit file in /etc/systemd/system/name.service and use .include directive. 

Suppose we need to add one argument to daemon binary in a service of type "Simple". Then we'd use something like this:

.include /lib/systemd/system/foo.service
[Service]
ExecStart=/usr/bin/foo -new -args ...

But this is not possible, because systemd reports an error, that we want to define ExecStart twice in a service of type Simple. But we don't, we want just re-define it. systemd should be able to do that, since changing arguments of a daemon binary is quite common task.

Version-Release number of selected component (if applicable):
systemd-195-7.fc18.x86_64