The primary thing you need to look for is if the light was rated for 3.7-4.2v. If it was, 2xCR123 will not work, and may actually destroy the driver.
If you have lights that are rated at 6v or higher, then 2xCr123 will be fine. Best way to know is read the specs carefully when you order the light, or better yet, order the drop-in separately and get one that serves both battery sets.