> [Can I] Upload 100GB of data to Google Drive?
Yes…is there something preventing you from doing so?
> Play movies stored on my external hard disc?
Well, you could if your hard disc supported a format that iOS could understand, such as a lightning cable, Bluetooth, or Wi-Fi.
> Download Youtube videos for local playback, as some Mac apps can do?
There are apps that let you do this.
> Can I build an iOS app? An Android app?
No, unfortunately you can't do this yet. This is one of the things that iPad cannot do yet and I'm sure Apple is working on.
> The OS and apps could and should be updated to support touch.
This is an awful lot of work for developers…especially on Apple's platforms, where bolt-on solutions are rare and most apps try to make full use of the medium they have.
> I want an OS with the full power of a PC OS + touch. You can get there by taking a mobile OS and making it more powerful, or by taking a PC OS and adding touch to the OS and apps.
Yes, we all do–and Apple is doing this from the "taking a mobile OS and making it more powerful" rather than "taking a PC OS and adding touch to the OS and apps" as Microsoft is doing. My argument is that this is the better way to do things, and the market seems to largely agree.