Andy, I think that a point to consider is whether or not the average user needs the biological filter function. If they need this protection, it would seem that once a year testing is not sufficient. Anything but a continuous process can fail to detect failure long enough to make someone sick. I do not know how many Zweeds there are in a filter, but you are probably right that a single failure may only be detectable by the tester.
Some alternate approaches:
Provide a sales contract, as an option to the buyer, that indemnifies you from the results of biological leakage for anything other than initial manufacturers defects. Clearly mark the unit (laser etch, different model/serial number) as not being tested on installation nor warranted for biologic filter effectiveness. With this contract, GE can sell to anyone who needs filtration but not biological protection. They don't need a local dealer, or yearly testing. If they need both the filtration and biological protection, and they do not have a local dealer, they can choose 1) convince a local dealer to take the line of GE filters (not so easy, but not impossible - I believe I caused a local water system dealer to pick up the Homespring line), use other methods of biologic removal such as chlorine, ozone, etc. as they would otherwise, 3) have nothing and maybe buy from ****. I suspect a lot of the potential users do not need the biological protection. They would be using the well water for drinking anyway, but it would look ugly.
There are also alternate methods of checking for biologic integrity. A simple culture based test using a readily available test kit can check at whatever interval the owner chooses. It would seem to me that including one of these tests in the box (or a card to send in to avoid shelf life issues) would deal with the installation. After that, let it be up to the owner to repeat this at whatever interval they choose. The alarm on the control would then be a reminder for a yearly test. Dealers probably won't be happy, but users, and people who want to be users but don't have a local dealer) would.
I am also a bit concerned about your comment of "throw them out" for the Maytag units. This sort of implies that if you have one that old it should be replaced. I have one. It has been installed for a few years; does that mean I should throw it out? Is there something about the preservative shipped in the filters that does not protect the fibers?
I might note that I can completely identify with people who need this unit but have no local support. When I got mine (and it was the only thing that would fix my clay problem (< 0.5 micron) I had to jump through many essentially insurmountable hoops. I found a reference to the product on a engineering web forum and looked into it on the Zenon web site. When I contacted them for a purchase I was informed that only Maytag sold them in North America.
Maytag listed about half a dozen distributors. All but one simply would not reply to email or return phone calls. Maytag was fully into the "disclose absolutely no information about the devices that may possibly be useful". You simply could not get a service manual. A guy at Maytag wanted to help, but company policies had his hands tied. There was one place on the list that was ready to sell me one (they were about 1000 miles away) but when he found out I was out of state he said state law would not allow the out of state sales of an "appliance". Zenon was very friendly, and I believe really wanted to help, but they had this really stupid marketing agreement with Maytag. I had a sense that some people there shared my view as to the suitability of a Maytag only channel. I have always been curious why Zenon would accept Maytag as the exclusive residential marketing channel. I would simply not think of a Maytag store as a place to look for high tech water filters. On the other hand, I don't think there are any GE stores. But if GE can get around the dealer only thing and get them into wider distribution, they could probably sell a bunch more.
I finally drove to Canada and bought one. No warranty or service of course.
I simply had to have one for my water to be usable.
While protecting us from ourselves is a nice thought, it is also not the responsibility of a product manufacturer to deny an adult from buying a piece of equipment they have determined fits their needs. I believe the contract deleting biologic responsibility I suggested above will take care of liability (probably a significant driver of the policy). I really think GE is more exposed with the yearly check. It kind of implies that it is OK for the next year if it passes the test. An implied fitness for use.
It is an excellent product. It fixes water that simply can not be reasonably dealt with any other way. But I do believe that the dealer only install and no warranty without yearly test is not appropriate in all (or any for that matter) circumstances. It adds cost and causes difficulties in obtaining the product in cases where it is simply not needed. It is moderately unusual for a consumer product to be sold with essentially a separately charged mandatory lifetime service contract. And make the warranty dependent on this service contract.
And no - I did not think the comparisons you used were appropriate.