Learning from your email, you are not very much familiar with the procedure of the crewing process in your company. Suggest you to seek for the advice from the available vendor in the market who will provide you the similar service; however it would be an expensive option.
The alternative is to hire an expert locally to study your internal process and make recommendation to you.
If you choose the 2nd option, I may be able to offer you some useful information.
Cheers