The whole point that him pretending to be rich is to get a date.
The whole point of this supposing to be a big wall is to hold off the barbarians.
The first one seems correct, the second one doesn't sound quite right - but why wouldn't it be possible to use the equivalent forms here?
I was thinking about
The point of this supposedly being a big wall...
but that clearly does't mean the same thing.
I am aware that one could say "The point of this being a big wall" even if the wall is not yet big, yet that doesn't seem to work in all cases.
The whole point of this supposing to be a macro is that it shouldn't matter where it is located.
This is the sentence I actually want to construct. I don't want to say "the whole point of this being a macro...", because that would too strongly imply that it is or should be thought of as one. Instead, the idea that it is supposed to be a macro is first raised, and then dismissed.