While some "neat to have" features, you cobbled together your feature list without considering the tradeoffs they bring. All of these features have been considered by product managers and cut for good reason.
Since you haven't owned an iPad, I'm guessing you're more price sensitive. Most of your features will add cost, size, reduce battery life, and will give you little daily benefit.
- Full-sized USB ports - tablet is too thick, heavy and added cost. Also, to support devices like USB sticks, you have to add USB Host support to the device, which requires adding a 5V power supply output to the device, most expensive/power hungry USB host silicon/IP, and a large USB host driver stack that requires lots of software maintenance.
- Full-sized HDMI connector - added cost and thickness.
- Stereo Mics - nobody cares, added cost, and they don't work well in a thin form factor - generally for field recording you want cardioid-type mics which are larger, but more directional.
- Hardware radio toggles - nobody cares, added cost, confusion (which switch does what by feel?!) and the functionality is already deployable through corporate policies on some ecosystems.
- Offline maps - There are plenty of offline GPS apps available for existing ecosystems - TomTom, NavFree, and Garmin come to mind without even searching. This feature is best left to companies who know what they are doing in this space. If it's standard, you have to have more storage standard on your device which raises cost. Whatever you deploy won't be nearly as good as Google Maps anyway and will be useless in a few years once the data goes stale and you are too lazy to do the update process.
- Pixel Qi or whatever screen tech du jour - These will come naturally once they are better, cheaper, more manufacturable, and lower power than the existing crop of LCD displays. The current crop of screens, at least on the high end devices like iPad are readable enough in full sunlight so it's not a big pain point.
- Alternative OS support - Who cares? Tablets are not computers. Apple was the first company to understand this and this is why the iPad was so devastatingly successful. They are devices that perform functions. Use a computer if you need something that's flexible and programmable. Adding alternative OS support adds MILLIONS in software support costs, and you're not going to sell that many more tablets as a result.