You must all be very aware of the maintenance involved in AED.
It is not enough to buy one and know how to use one but batteries and pads need to be changed roughly every year and the software tested. AED outside hospitals have sadly a very high failure rate not because of poor training of the public, but for lack of maintenance of the device which then doesn't work. This is something you must discuss and contract when buying one. The maintenance cost is quite high, around 400 - 500 per year for the most basic devices.
This might be one of the core reason why there are not so many around. You can't just buy one and put it on the wall. A person has to be responsible for it and needs to schedule maintenance. I know this because years ago I was a safety and security manager and I was the person in charge for this. Also, going for the cheapest one, manufactured with poor quality parts (cables, ..) is not always the best idea.
So, the key for you to succeed , OP, is to be ready to solve the buyer problems, because, soon or later, maintenance is the objection you will receive.
Another issue about AED is where are they located, do they need to be kept locked (shopping centre) or unlocked (office) and then who has the key , you also need to train the personal not only on how to use it but to remember to use it in case of need. Especially in big companies, where you might want to have one at least every two floors.
In my experience, you shouldn't avoid the training. The personal needs to be trained not so much because they need to be trained the use of the AED but otherwise they will not use it in fear of killing someone. Which of course cannot happen, because the AED takes the decision away from you, but they don't know that. And worse, very often an AED is available but people are shy and prude, so they won't open the person's shirt, or expose the chest by lifting the top, especially in women. It is not a gesture that comes naturally to us. If you boss or the CEO collapses at your feet, it takes some guts to rip the buttons of his shirt or worse HER shirt, lift the bra exposing the boobs, and apply the pads.
Training in CPR is also essential,because that's where it starts. You do CPR while someone goes and bring the AED, then you still MUST continue CPR while the pads are applied and the machine is turned on, only when the machines tells you to stand clear, you stop.
And the very very first thing you do, before starting all this is call emergency services.
People should also know that they are case in which the AED will not shock. Some good reason such as there is pulse but also sometimes because the victim doesn't have ventricular fibrillation or ventricular tachycardia. And the person applying the AED can become very distressed because he might think he is doing something wrong when in fact the victim is beyond the point in which shocking him wouldl save him.
I am very sorry for your nephew OP and I love your initiative.
Maybe to have more exposure, why not make a video in a public place (shopping centre after closing hours) of what you need to do in case of emergency. Call 999, check airways, expose chest, CPR and AED. And let it cascade through the emails and forums. And at the end of the video, talk about your story and why having AED around may save your life. People are more likely to forward such a message.