... Buy some Home Magazines. Some attics are limited in what you can do w/them. From here, no one can see your attic to make any suggestions. AND, the existing structural components need to be considered to see if they can hold things like - the whirlpool bath or the waterbed, and so on. It's not that simple.
You do need professional advice. From there, the $$$ you spend on hiring an Architect can be saved on things like painting and trimming and so on in your new Master Bedroom. Maybe others have some ideas.
My best to ya and hope this helps.
PS: Hiring a pro in a situation like this is $$$ well-spent. You don't want a situation where your whirlpool ends up on the 1st floor, do you? You'll end up sitting at the table w/your insurance company trying to explain it to them where you could have been sitting w/an Architect and learned this before hand. Load requirements ARE a consideration here.