I understand what the current "octopus" implementation of legato is, but I don’t see how it can be useful on most synthesizers… it would result in a hung note (?)
On fingered legato, the notes just have to overlap, but the first note still must have a note-off. This is the way most monophonic (303 clones) implement slide. If no note off is sent for the first note, then the synth will slide back to the original pitch after the second note-off is received.
Again, this behaviour is probably as simple as adjusting the LEN of a step so it ends at least 1/192th after the beginning of the following step.