That's exactly what I did last year :-) A stand alone sediment filter where I turn two valves to reverse the flow of water. It's not very aesthetic and it takes more space but it does make my life easy.

Regarding your 2nd point, most of the cartridges use a "Welded Housing" and carry the "Dow Filmtec" brand. However there are sellers on ebay that supply housing that can be opened and you can fill your own filter material. I'm a little skeptical on taking this route without an understanding or testing ability of what effect it would have on drinking water. I wonder if there's an off-the-shelf complete water test kit or a lab that would do that for me.