I can understand your concern given your prevoius experience in your friends wedding. That was a really crappy thing for her to do to you.
Now you asked what you should do and my answer to that is:
Talk to the people you want in your bridal party, explain to them that you want them there, tell them you know it is a lot to ask and you understand if they can't do it and give them some time to make a decision.
Your wedding is a year away so there is no reason to rush into getting BM dresses right now. Give them some time to make their decision and make deposits on the trip. When it gets closer to time to get the BM dresses you should have an answer about who is committed to coming and who is not.
The biggest thing is to talk to them, don't pressure them, just talk to them about whether or not they can really come.
Most people will assume that, being a BM, they will have to buy the dress and such. It is a very common practice. Don't tell them you are paying for it, leave that as a surprise for when it is time to buy it. As for paying for their rooms, maybe that is something you could work out with your TA, that way your friend would make whatever deposits are needed and when the rest of the payment is due you would give the TA the remaining balance. That way if they were to back out you haven't paid anything for it.
I'm not sure about the whole photographer thing. Are you paying more for them to do the extra pictures for you?