One things for sure the new defenders will not be repaired "in the field".
I agree with Carson G that it very much depends on what breaks, and it was ever thus. In addition, we often don't give enough credit to how much more reliable the complexity of computers has made our vehicles -- yes they are a bit harder to fix, and they can't always be made right with chewing gum, a buff, and a good attitude, but they tend to break a lot less in general than the "simple" cars of old. This is true for other vehicles too -- My motorbike has over 6 figures on the odometer (a feat that would require engine rebuilds for my father's generation of motorbikes), and while it's very complex with sensors, ECUs, and digital stuff, it's also very field-repairable. I just need to have the right tools with me, which in the case of my bike (and the Defender) includes some kind of computer (i.e. a smartphone). Where the Defender has a few gaps is in the software -- but, my bike experienced the same gap when it first came out, and the aftermarket responded with affordable software to service the vehicle. I'm sure the Defender, with it's following, will have a similar aftermarket solution eventually.
However, your comment has reminded me of one of the more positive takeaways from the TFL saga that has not yet been mentioned (that I saw). I promise I'm not just wearing rose-coloured glasses with this thing -- they should never have been in this situation with a brand new vehicle, and there's no debate there.
But, the TFL guys experienced a problem serious enough to apparently require a totally new motor, and yet the Defender made it back to the dealer under its own power. It did not trigger a limp home mode, and it did not just "sit down" at the first sign of a problem. Translated to "real world" applications, that's actually good news. I was genuinely worried about getting stranded in the event of an issue, but I'm less worried now. This has not been true for all JLR vehicles; I have personal experience with a Jag that would sit down and not move anytime there was a trouble code, for instance, and I know that's not unique as I've heard of similar stories from other brands as well. Again, it shouldn't have happened after 150 miles or whatever. But, all vehicles break eventually -- imagine a Defender after 200k miles on it throwing a similar code while you are in the "back-of-beyond" due to a failed coil or plug. It's' reassuring to have some evidence that when the vehicle fails, it will at least get you to the "front of beyond" and not leave you stranded. This is a case study of one, so it's far from conclusive, but it's still reassuring in a way and sheds a tiny bit of light on the "how it breaks" question.
I did not listen to/watch the full 50 minutes of that TFL podcase -- if someone has and can post up any "new info" or a summary that would be super handy.