Also heres some good features to add :
1/ the ability to send and recive private messages before and after the job has been awarded, its very helpfull to ask questions that buyers may forget to include on their project description and also to keep track of the work after awarding the job (it help the admin to see if the freelancer or the buyer trying to pay outside the website)
2/ Invite freelancer : allow buyers to invite freelancers to apply for their jobs and the ability for admins to set the cost to apply for invited projects.
3/ Replace the current header with slider one (revolution slider is the best plugin for that)
4/ Allow freelancers to provide services (exactly like what taskerr theme do, that mean HireBee + Taskerr)
5/ Allow freelancers to feature their services to be on top page.
peopleperhour freelancer website is a great reference for the features i mentioned.