It would be great if there was an option to customise the piano settings like the other instuments. In fact to customise it to individual requirements can't be that difficult to achieve? eg set the note range in both clefs - this would allow any 5 finger position to be set, have a pick list of rest and note types (minim, quaver, triplet etc), whether to have chords and if so how many notes in them. In this way you wouldn't need levels, you could just set it to what you need and this would allow introduction of say triplets to what you already are comfortable playing, then add another note to the note range etc. etc This would make the whole experience VERY incremental and suit individual needs.
Agreed. The idea of practicing with chords is very important, because they offer a very specific visual coordination challenge to the piano sight reader, and one can't become a proficient sight reader without them.
And in addition, of all the suggestions for improving the piano sightreading possibilities, adding 3,4, and 5 note chords would probably be the easiest to implement.