If you were to choose the new companions...

I can see where you are coming from but apart from their different starting point in the Crows, they do have some similarities in their character, although you might not discover this with Zevran depending on which missions he is with you for. For example, he does have principles with regard to the enslavement of the elves in the alienage and makes this clear if he thinks you are considering doing a deal with the Magister. Because he never had the same status as Lucanis, he couldn't exercise the same degree of discretion that Lucanis does in TN. However, the fact that Illario keeps objecting suggests that not only is this not standard Crow practice but that Lucanis has never previously demonstrated a social conscience.

As far as training went, whilst his grandmother may never have allow him to die through his training, it was tough, almost cruel at times, although Lucanis acknowledges this was likely to ensure his survival in the future in the highly competitive and ruthless organisation of the Crows. To that extent, that is only what they are doing with their slave recruits; it is survival of the fittest, with no room for sentiment. That is the true nature of the Crows. Both Zevran and Lucanis need the opportunity to see something outside this sort of life for them to consider leaving it. Zevran originally considered suicide because there did seem no other way out for him and, to be honest, if Lucanis has faked his own death, that is pretty much the same.

Now I agree that Lucanis could be developed along different lines to Zevran as a companion and, on the evidence of TN, he does seem a much darker, colder personality, although not without a sense of humour apparently. It does depend on the writing. There is certainly the potential there for a really interesting character development but they need to avoid relying too much on the flippant side of his nature to make him sympathetic to the players, particularly those who have never read TN. That is what I meant when I said he could just be Zevran 2.0 if they are not careful to make him distinctly different.

Another thing which could be a factor is that with his voluntary relinquishing of his status in the Crows, Lucanis would be effectively starting again from nothing, albeit with perhaps some useful contacts in the Tevinter underworld.    If they are still pursuing the stated theme of the Behind the Scenes video of what it is like to have no power  (other than your own abilities) perhaps this related to your companions as much as the new hero.   Thinking about it from this perspective:

Davrin is a Grey Warden, whose HQ has come under attack and is likely pretty much destroyed.   Any security he once had in that organisation has been shattered.
Bellara is likely from a faction which either has little power or has been exiled from it, for example a Kal-Sharok dwarf who has been banished.
Lucanis is Crow who faked his own death in order to escape the destiny his grandmother had planned for him but is now without the security of his status within the Crows.
Neve is someone who runs outside of the usual avenues of power in Tevinter and so has no one she can rely on but herself.
Mateo is a Lord of Fortune, a freelance treasure hunter, whose guild carries no particular political clout and whose members thus have no real status in society other than with each other.
Maevaris is an Altus who family seat was in Qarinus/Ventus and thus is currently under Qunari occupation, so may well have lost standing in the Senate as a result.

You see the general trend I am working with.   Look for a potential companion that either has no status in society or has suffered/will suffer a fall from grace from the status they once enjoyed.