I have a typeface I've developed that comes in two variations, one spans horizontally whilst the other vertically. At the moment they sit as two OTFs. What I would like to do is create an OpenType feature that would allow for variations between the horizontal and vertical in the same usage. E.G. I type a word, the first letter is vertical, the second horizontal, the third vertical etc etc.
The reason I ask this is to avoid having 4 separate faces which you would have to switch between to get the same effect, rather than an on/off option. What level of scripting is possible inside OpenType to do this? Is is possible or am I still looking at having a set of 4 fonts with which to implement this with.