Ivan, of course, started out as the foil for Miles – he was everything that Miles was not – including dense. But Cetaganda and especially A Civil Campaign developed his character significantly more – Ivan is in many ways a leading character in the latter book.
With a wealth of interesting characters with in-depth personalities, Lois seems to have one or two (other than Miles) whom she focuses on in each book, using the others, in character, as “background” until she’s ready to work with them.
It’s also interesting to see the little connections linking each story to the others. Did anybody besides me happen to catch the identity of the jumpship pilot whom Cordelia maneuvered into assisting her in escaping Beta Colony towards the end of Shards of Honor? (Hint: he’s a major supporting character in *The Warrior’s Apprentice.) And the fact that most of Diplomatic Immunity takes place on Graf Station, which includes the Minchenko Auditorium – both being named for important characters in Falling Free, set 200 years earlier.
Further interweaving takes place here and there – the Haut Pel and Gen. Dag Benin play roles in several different stories, for example.
And I wonder what’s lying in wait in terms of loose ends, that Lois intends to weave back into the tapestry in future books? What, for example, are Mark and Kareen up to? What happened to that psychopathic dwarf woman commander of mercenaries after The Vor Game? What are Elli Quinn and the Dendarii (band name if I ever saw one! :)) up to these days? And what role are Count Dono Vorrutyer and the Imperial Auditors other than Miles going to play in future stories?
Odds are pretty strong that Lois has all this stuff figured out – and is keeping it close to her bosom until the time is right to reveal it.