Yes, that is the sort of thing. There are commercial systems that do that; including water-adjusted metering. I would like DIY, but knowing a reliable equipment brand would be helpful. My wife is not into things that need operating attention and maintenance. When I die, she does not want to be stuck with stuff no one but me can fix.
I don't recollect the material offhand while sitting here, but there is at least one material that tolerates a fairly wide range of ph, locks both flavors of arsenic, and can be disposed of as normal waste. It can be reactivated, but it is a real annoying process, best left to proper facilities. It is, of course, very expensive. There are a number of systems sold as services. Many that I have seen of the service variety, use a dual tank system to protect from breakthrough, and regular arsenic tests. They seem to send some of the materials to a re-activation facility so it is a bit friendlier to landfills.
My ratio of iron to arsenic is sufficient that oxidation may be able to precipitate it. That is certainly an alternative I am looking at. I am not sure how much of the iron may be bound by other water contents such as a clay. I need to experiment. I have an ozone generator around someplace.
My primary issue is to fix my water. An additional goal is to find a couple of core components that could be propagated with volume discounts as a community effort.
There is lots of alternatives. In addition to a technique, the problem I have is in choosing a reliable vendor/manufacturer. Techniques are relatively easy to find and understand. There are bunches of government and academic comparisons of media. Some real interesting techniques developed at some universities, but with no disclosure of sufficient information to build a system. There is one system that uses electrical currents to migrate the arsenic to a collection material. Very inexpensive in terms of construction. Their proof of concept system cost them less than a couple of hundred dollars to build. But they won't disclose any real implementation details. Low maintenance requirement and very little operating cost. Their target is the third world; but lots of these types of people seem to forget that there are people here without a lot of money as well.
What is lacking is publications of independent evaluations of specific equipment and vendors.