Advanced Push modifier

[DoonBarrum]

This is allerady possible by using CAT muscles:

MusclePreview

Use a skin wrap to apply it to your mesh.

I don't see how that can achieve the same result? Once skin wrapped the vertex data is set and it applies to the initial setup. You are unable to f.example drag a muscle through a tube and have it push in multiple places, it will only drag vertexes from its original position. 
Also, you are unable to select any object, if the push modifer would support any selected object as the push normals you could basically drag a teapot through a tube and have the tube conforming the teapot.

What you are describing here is what tyConform can already do.
With the muscle preview I just wanted to show you that you can conform muscles to objects by using them as deflector. Cause you intentionally asked for muscles. Pulling a teapot throug a tube is not an usual muscle usecase .

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Okay sorry, the tyConform doesn't do the job. It would need some option to reverse direction to do it.

But I made a quick flow setup that almost does the job:

Hi thanks for the TyConform suggestion. Actually I tried that also, it works slightly with some objects, like a cylinder with no ends, but it breaks if you move the object slightly outside - so its a half good solution it can solve some situations, but a push modifier with support of other objects could be very useful in many situations.