Options for Requestors other than full licenses

Hi -- I'm looking for any ways to reduce the number of full licenses I need.  We just acquired another company and could potentially be increasing users by 50%.  Some of my project managers/job requestors have less than 10 projects in Wrike in a year.  Basically, they would need to be able to fill out our custom request form in Wrike, attach files for input, review files and comment on or attach files for editing.

Does anyone have any suggestions on how to achieve this without adding full licenses for these "once-in-awhile" users?  Thanks!