I'm not sure if the term "40k formula" would be correct. Yes, there has been a constant development/evolution of the basic rules, but I'm not sure it would be correct to say that DW is "outdated" - simply because these books (very much like the rest of the franchise) do not represent a uniform, consistent approach to the setting, but rather a more focused, perspective-based take, hand-tailored to the theme they serve. For this reason, every game has a number of unique mechanics that are present only there, such as the Squad Modes for DW, Comrades in Only War, mutations and rituals in Black Crusade, etc.
That being said, if you really like an aspect of another game - such as, in the case of Black Crusade, the freeform leveling - then by all means, try and houserule them into your DW game! If you go with the BC rules as a whole, though, be prepared to miss out on various DW-specific mechanics, whilst simultaneously having to deal with other, new features designed for use by heretics rather than loyalists.
And on a sidenote .. I think that, in a way, DW is meant to be "not very balanced" in terms of allowing the player characters to kick all sorts of butt, even moreso than in any of the other games. It's a special, thematic approach where Space Marines are portrayed as incredibly powerful gods of war, rather than a more nuanced version you may find elsewhere.
You could compare this to how two different novels portray an army, all depending on who the protagonist is, and the author's own preferences.
If you expand on your feelings regarding the things you criticised (what you mean exactly when talking of streamlining, logic and balance), perhaps people could offer you more constructive advice on how to proceed?
Edited by Lynata, 23 June 2014 - 04:26 PM.