A few points.
"today's app stores prevent us from having a direct relationship with the app developer"
Have you tried walking into Heinz HQ recently and buying a tin of baked beans? You can't, and it's because there's this thing called a 'channel' and has these things called 'resellers' and it applies to a hell of a lot more than just apps. Some have one, some have many, but there's nothing new going on here.
"Once an app store vendor bills you for a set of apps, it's hard to justify purchasing them again on another platform." and "I'm married with four kids: I can't afford too much app divergence."
You can't have your cake and eat it, mate. You allude to taking advantage of the fact that you can install a single purchase iOS app on multiple devices simultaneously, and then you bemoan the fact that this isn't cross-platform as well?
Nobody buys an Xbox expecting to be able to get their games exchanged if they replace it with a PS3. Nobody buys spare parts for a Ford and expects them to fit on their new Fiat. Nobody has four bloody kids and expects to get all their clothes ugraded to larger sizes when they grow out of them.
You choose your platform, you buy for it and you make your investment like you do for almost anything else... until it's time to change the lot. It's preposterous to expect the entire software industry to go out of its way to cater to your principles on portability because you're a bit of a tight arse trying to save yourself 59p. You'd be better off giving Heinz HQ a ring and using condoms.