First off, don't let anyone discourage you. That's got to be rule #1 for anything you try to create.

One of my brothers heard "It won't work" and "Good luck with that" about a zillion times while he was working on a new type of baby bottle. It took several years of hard work to get it off the ground and into stores, but shortly after that Johnson & Johnson bought his company and rebranded the product. My brother was compensated quite well, and those that discouraged him were mostly silent about that.

The expensive part of your project are the dies to make the plastic parts. After speaking with almost every plastic injection company in the U.S., my brother ended up going to China to get his stuff made. All the U.S. companies told him "Can't be done", so work past that too.

I like your concept, especially a rotating pump as opposed to a push/pull pump.

I don't use a bladder system, but I'm all about innovation. Perhaps you could make the pump/filter as a self contained unit that attaches to different style bottles. If it was smaller, or lighter, or faster than a "Katadyn Hiker" you've got an advantage right out of the box.

So I'm going to encourage you to keep working on your plans and offer my best wishes for your success.

Please keep me posted on your progress!