Well, having an encrypted storage that uses interleaved blocks for storage would allow you to have multiple versions of the data at the cost of 2x (or #x) the data storage of the largest partition. You could even throw in some parity to make the image resilient to damage. Software could then use the key provided to find the set of blocks it opens. Software wouldn't need to know anything beyond the basics of block size and number of parity blocks after it was created. Each read/write would read all the parallel blocks at once and write them all at once. All watching that would do is let you know which blocks changed. And that is assuming you can observe usage beforehand. If not, then you have no idea how many real data partitions there are or if you were given a bogus password. That being the idea behind plausible deniability.