Does this replace the planned third part of the trilogy, the AMG /
Invisibles (?) crossover? Or is it just another branch of the story, borne
of a need to write more John Constantine? In either case, right on, can't
get enough, etc. etc., and on with the C & C....

Nah, this is actually far down the line as far as things go.

Consider this the last Hellblazer/OMG story I'll ever do,
since the ending of it is a little, eh, well, you'll see.

There was a tortured scream, a demon's roar, and suddenly
Bill exploded in a shower of ropy innards, torn flesh, and
so much red...

    ....wasting no time at all in getting into the heavy developments. I
guess I was expecting a little more light banter first, since it's kinda
hard to move in that direction once you've blown someone up and made it
Skuld's fault. I fully expect a long and funny epilogue for this, now. :)

Sorry, there won't be much humor in this.  The Faith Machine is
going to be more serious in tone than Dire Fates, maybe a little
bloodier, definitely with a more somber end.

-rod m