It will work just find with out the drive in. You can also get a optical bay hard drive adapter and install a second drive with it: 9.5 mm PATA Optical Bay SATA Hard Drive Enclosure
Add a hard drive to your laptop by replacing the optical drive with a second hard drive. Compatible with all MacBooks (excluding Early or Mid 2009 MacBooks, MacBook Unibody and MacBook Air) and all 15" MacBook Pros (excluding Unibody). 9.5 mm Internal ATA — 50+ available at 39.95 each.