The short answer is yes, you could.
However, you would be missing out on some of the most valuable elements of Clarizen.
First, your resources would not be able to report timesheets. Further, they would not be able to partake in any of the collaborative features that Clarizen has to offer.Their influence on the project would be minor.
If you were to acquire Team member licenses, or time & expense, your users would enter Clarizen, participate in discussions, would be reporting timesheet. They'd share and collaborate on files and customers. The project team would have one platform to work together on the projects and tasks.
There are many more advantages to having users actually in your system, and i advise you to discuss these with your account manager and customer success.
Please note that you may also invite users, who will automatically get 2 weeks full licenses before you needing an actual licence.
You can use this period to work with your team inside Clarizen and see the value.