All right, so here's the longer thoughts I promised earlier.
1.) I think shifting down to one piece of hardware makes the most sense, and their console line was the obviously super dead and redundant product line, so a handheld that outputs to a TV is the best fit from that perspective. This was the product line suggestion I've been making for a few years now, since it's both easier to support, easier to release new iterations of with minimal R&D costs, and at least has a theoretical target audience, and I think it still makes sense.
2.) Tegra means it's going to be a high end, modern feature set handheld more akin to what Sony did with their handhelds than what Nintendo has been doing recently. High end console game ports feel like a more dubious proposition, but anything you see on phones, handhelds, or the type of mid-tier games you see out of Japan should all fit fine. I'd imagine it's a pretty nice target for most indie titles as well. It should also trivially support all major engines, with the requirements of the games running on the engines being the main question. I suspect anyone coming at this device from a handheld perspective is going to be really happy with the hardware, while console gamers will be more of a mix bag. I would expect graphical improvements over the Wii U given the much more modern hardware feature set and that the Wii U is so ancient that mobile hardware in a handheld should be able to power past it, but I don't see a scenario where this compares to the Xbox One. Rendering on a handheld screen will presumably look a lot more impressive than a TV, and would almost assuredly be my personal preference using the device.
3.) I don't think losing BC is an issue. This generation made it really clear that you want to make the correct hardware choice for the future instead of the hardware choice that allows you to run last generation's games. If I were a console vendor, I would make this trade-off every time (unless the correct choice just happened to let me run old games easily anyway).
4.) It's a handheld so obviously physical discs are a non-starter, so cartridges make sense from that perspective. 32 GB cartridges could potentially eat into margins, but presumably games are largely going to be $60 from now on, and that should offset the cost. 32 GB is a bit tight for high end PS4/XB1 games, but again I'm not convinced getting those is the main goal of the system.
5.) The base station with TV out makes sense since it's presumably also a charging station, and thus you don't have to worry about power when using it as a console. I'm curious to see if it can upclock the processing speed when connected to a power outlet to help with any potential resolution bump, or if it just is a power charging situation. I think either scenario is fine and won't really make a difference to the platform's situation, and is more of just a technical curiosity.
6.) I'll judge the operating system when I see it. Not being Android is fine if it works well.
7.) September is a fine reveal window. That's six months before launch, which is about how long companies spend advertising their games these days anyway.
8.) The detachable controller thing sounds fine. I don't think it's some amazing selling point, but it lets them sell one unit that conveniently fits both form factors without it sounding like a nightmare, and that should be considered a win.
Overall I'm optimistic about the system from a personal interest perspective. It will be nice having Nintendo hardware that is actually modern for what it is. I need to see a bit more to get a sense of the potential market situation, though it's hard for me to imagine a handheld in 2017+ that sells more than the 3DS did overall. It does sound like something that would do quite a bit better than the Wii U however, if only due to handhelds being way more popular in Japan and way more accessible and appealing to children in the West.