Unfortunately, because were only using RAID0 we do not have the ability to swap individual array LUNs in and out of a RAID Groups as we can with regular spindles. As long as this LUN was reasonably close in size, it shouldn't be a problem. Differently sized LUNs are only a problem as the aggregate fills up. If one LUN is much smaller, it may fill up first. If there are no free blocks to write to, the IOPS that LUN would provide on write operations are lost. So it can potentially affect performance.
Hope that helps!