Thanks Mike
I need to do some further testing, but when I was experimenting with 1.1 node, pluging a bump map into the FG material, turned it blue. (was a pinky red colour).
I'll post an object and scene if I can repeat what was happening with 1.1b
Haha, you are pushing it, aren't you?

Bump connections store the perturbing vector within the RGB data, basically:
final shading normal = initial geometry normal + bump
So the RGB data will store values between -1 and 1 in each component, depending on the direction of the bump.
Merging bumps would thus require different code, and you could probably only do a blend, none of the other blending modes (you'd need to do that to the image before the perturbing vectors are extracted from it, which is before the 3D image node sees them).
But hey, at least allowing for simple bump merges sounds like a nice feature request!
Cheers,
Mike