You know, this makes me wonder of what Blackheart cgi/makeup would be better. There's a recent japanese movie named "Devilman" (based upon the manga Mao Dante by master Go Nagai) about a man transforming in a demon that, despite the excellent CGI, has too much strong differences between the live actor(even with quite good prosthetics in a "intermediate" form) and the cgi actual demon (an issue determined also by the scene mounting).
I fear a similar effect about Blackheart , if they decide to make the real demon form totally cgi. Maybe just some slight modification (a tail, a menacing, growing shadow with spikes, hair moulting sometimes with spikes, Wes with Blackheart's face only when in shadow), just some hinting elements during the film would be: first, more in line with the character; second, making continuity actor/cgi; third, that would keep the real BH form for the finale (quite like...omg maybe it's unlucky said that...Spawn o_o; ).
Anyway i think BH cgi would be very effective if played in the "living shadow" theme...