OKAY.....I had one of those change of plans, which happened to occur in line waiting for OCC.
Basically, G1 Slog's combined torso mode has a shape that is eerily similar to that of Combiner Wars Prime when you don't open his chest. It's spiraled out of control from there.
I decided to use Firefly as Wildfly, and Armada Megatron's head as a base for the Monstructor combiner head.
And yes, the articulation still remains from stock, and will have the elbow as well
And Slog's monster head will be a modified FoC Grimlock head
EDIT: 10 hours later....
Bit better look at Combiner torso mode
Slog's robot mode
....Yeah any suggestions how to make this monster mode look better, I'll take them gladly
Wildfly V.2 robot mode
Wildfly V.2 "bird" mode
Wildfly arm mode