Re: Camel back plus chest pack
Not exactly an answer to your question but perhaps an experience you may find helpful. I'm a vest to pack convert so that may play into my opinion.
I owned a Fishpond combo pack and used the whole thing together for one trip. It clipped together and didn't require another strap around the neck, but I did not like having that pack right in my way at the center of my body. I used the backpack more than anything else until I parted ways with it. Great pack, it just wasn't for me. I prefer to have a pack that fits behind me or on the side of me these days. I use a waist pack and a sling pack. Have not worn them together, mostly because I haven't felt the need to use both at the same time. Though I can see myself doing just that on an upcoming trip. That way I can take off the sling, lay it on the bank and use the waist pack for the essentials.
Now I know that many people like chest packs but I'm not one of them. These pack options seem to have such a diverse opinion. People buy them figure out it's not for them and move along to something different, just as I did. I can tell you that I agree with your comment that what you're inquiring about would be too many straps for me to deal with. Sometimes I wonder if the vest wasn't the best way to go to start with LOL. I'm happy enough with my current setup though and certainly recommend that as a consideration.
~*~Leave only your footprints~*~