Regardless of your route and your source of surface water, the idea of a water filter is sound. Coffee filters and water tabs will only remove larger contaminants and kill biological contaminants. True water filters will remove physical, biological as well as chemical contaminants. They also have the advantage of needing only one bottle. With your proposal I believe you would need 2 containers... one dirty to gather the water and one clean one to filter the water into and treat with the tablets. In the end it takes up more space in your BOB plus you have a higher risk of filter mistakes/contamination.

JAB

I've been using my MSR Waterworks filter for years, drinking water through it from both lakes Erie and Ontario...and watercourses in between with no ill effects (can't say the same about water from certain restaurants).

My only beef with this filter is the ceramic filter. I'm paranoid of breaking it.

I've used the tabs too, but I tend to forget about them and they expire on me.

I forgot to mention - those filters are expensive! I can put a package of tablets in every bag and vehicle, but I'm not gettting multiple filters anytime soon.

JAB - didn't think of chemical contaminants.

Considering that you can only live about 3 days without water, dedicating space and weight in your BOB for a good water filter is a necessity.
In addition to water filters and purification tablets, there are also products like the Steripen.

As JAB said, the three concerns are going to be particle, biological, and chemicals in your water.

Coffee filters(Try espresso filters) or a bandana, with iodine or water purification tabs will take care of most particle and biological concerns.
Different tablets protect against different things. I use the Katadyn Water Purification tabs myself.

A Steripen will kill biological content in the water as well, using only UV light, so there are no additives to the water.

The only way to protect against chemicals is with an active carbon filter.

A benefit of the Steripen and a water filter, is your water is immediately safe to drink, without having to wait.

You can buy a filter system that is lightweight, costs $80 or less, and will go thousands of litres of water over its life.
At the very least, you can buy the filter straws for $11 off of amazon, and they are rated for 75litres of water each.

Activated carbon info and a few other tech. I cant find the topic where I had a list of the manufacturers.

http://www.home-water-purifiers-and-filters.com/water-purification.php

The way I see it is you need to carry both. There is nothing worse than drinking bog water that has only been filtered with a bandana or coffee filter. My MSR filter takes care of most of the taste issues, it gives me safe drinking water and its fast. I can peel off one litre of water right into a Nalgene or into my bladder in 2-3 min. No waiting for 30-60 min for the tabs and then worrying about contamination of the storage container from dipping it in the water source. My buddy recently got sick on a 3 day expedition where they used Steripens for the first time. They were scooping water from a stream into a Nalgene and sticking the Steripen inside. They forgot about the contaminated water on the threads and lid and a few of them got sick 12 hours later. I carry a couple dozen tabs for the inevitable point where my MSR will fail due to a broken filter or critical part. I think you really need redundancy for the most important part of your kit. Considering I have a nested Ti cup on my Nalgene, I have 3 easy ways to get safe water.

About the lowest cost effective filter I've seen is a Berkey sport bottle. For $30 it will do a great job of filtering the 700ml capacity about 500 times before a replacement filter is needed. Not so great for someone who camps a lot but it's the best I've found to stash in a BOB or car kit.