Hi AverageGuy,
I agree with starcorp re your option 2 being, at present, the most realistic application for Cubasis. This is not just down to the features of the app but also the processing power of the iPad (I’m using a 3rd gen model). That said, I suspect both these limitations to shift over time…
The other thing that will clearly influence how people feel about the various items on your list - and in particular option 5 (it would be great to be able to achieve this) - will be what other recording environment a user has available to them. If you are fortunate to also own a desktop system (running Cubase, etc.) then, at present, I guess you would not choose to ‘finish’ a project in Cubasis. However, if you are new to the whole multitrack recording world and your iPad/Cubasis is the tool you rely on, then I suspect you will just work around the limitations (e.g. no mix automation) to get the job done. The iPad/Cubasis combination is still pretty impressive stuff and way better that the Teac 144 I started my own ‘home’ recording experience on way back in the day 
Best wishes,
John