Hmm... That's more difficult then, I feel.
I'm not really an expert in this field, so I may bow out of the thread at some stage.
However, for now: are you targeting 'phones or tablets? I ask because this affects the amount of screen-space available for touch-controls, and perhaps how the user is likely to be holding the device and thus what controls are likely to be comfortable.
Well, i'd like to target pretty much all mobile touch devices but I probably have to go with the larger phones and up since yeah, screen space. The orientation of the device will be based on what is practical, with some kind of virtual analog stick the most practical seems to be landscape orientated.
Currently I'm experimenting with basic click movement, locking on a target and fire weapons. This is practical but not really how i'd like the gameplay to be and if I want to have somekind of turning mechanism then the play cannot really control these turns.
It pretty much appears this is to much to ask from a mobile device but I'm still open for suggestions.