I don't think anyone would mind you throwing in some shiny claws as long as you're honest about it's equipment. Though in ridiculously big games WYSIWYG makes life a whole bunch easier.
On another note: CLAAAAWWWS
I've ended up with the same first carnifex as yourself, and I built my second with stalons / crushing claws A: because it looks awesome, and B: worlds best can opener provided it can catch the can.
These fine gentleman are correct though, the twin - twin linked devourer with brain leech worm carnifex or "dakkafex" is absolutely wonderful, and easily more competetive than my builds.