Actually using this to get your ticket and experence then going somewhere else is the best most logical method for a pilot I have seen yet on the thread.
To be honest the salary isn't that great our TP FO's get more.
You will get the bonus of the tax breaks so it is worth it.
Command is bloody brillant to be honest its when flying becomes fun again. You get to set the tone of the day and life becomes extremely easy in my experence.
20 years as an FO sod that although with the size of the crew base you won't be flying with the same special needs Captains week in week out.
Use it for yourself you don't owe BA anything once you have done your time.