Actually, following up myself...
You would need not only to convert someone else's push into a vertical component, but actively having an upwards component without yourself at all times (really a downwards component within yourself than creates a resultant upwards component). Trying to establish a vertical component upon contact is really really hard to do unless you don't already have one set up.
How one is grounding a push is half the answer, the other half is changing how the other person is generating their power, as they have the same biomechanics problems with horizontal power. (Maybe this is why you are saying too?)
Vertical power into the ground is great as the ground can 'push back' with effectively infinite power (it holds up sky scrappers and mountains with little effort) or alternatively redirection into the up direction can store energy (as a raised mass = potential energy)