It might not take as long as you think! The last Black Ghost I kept grew from 3" to 14" in a bit over a year. And to avoid being flamed I'm not going to mention how small the tank was!The tiger barbs should also be fine, ive got a dozen living with a 8inch ghost. At the moment he couldnt fit one in his mouth, but i really dont see it happening in the future anyway.
The smaller tetras will most likely be a meal however, my ghost wiped out a school neons in one night, and this was when he was only around 4inches.