Hey guys. I'm wondering how you would approach the following problem.

I have mesh (A) and I need it to react to a metaball, primitive, volume or polygonal geometry (B) that is located inside the A in such way, that it pushes A's points outside of its point or vertex normals (if vertex normals are present). Sort of like inflating the mesh from the inside, but in a different way than can be achieved with bulge SOP because this particular SOP pushes the points of mesh A away from the centre point of the affecting metaball (B).

To clarify, you want to move points in (A) along their normal, with the distance being determined by weight calculated from (B)? For metaball/volume (B) the weight is well defined, but for polygonal (B), I'm not sure how you want to determine the weight. Distance to surface is about all you can go off of, unless some other attribute is present on the surface.

I recommend using a point vop, or wrangle depending on how familiar you are with VEX, to accomplish this. There are probably other methods, but using attribvop/wrangle is the most direct.

while it's not entirely obvious from its name, the Muscle Deform Sop will deform a mesh as you've described.

Excellent. The Muscle Deformer gets the job done.
Many thanks for your help!