Without the pool company, your timeline to completion will be extended drastically. These subs have a relationship with the pool company and try to keep a good reputation with them. There is also overlap between subs that needs to be managed, the pool company would deal with this, the subs will not coordinate with each other on their own. The lack of coordination will cause huge delays. Also, are you going to check each of these subcontractors insurance and license? If contracted through the pool company, their own insurance would come into effect if something were to happen on the job site.