You're really not enough providing enough explanation
For how your anti-99% attack system would operate.

Look, either the best chain is the one with the
most cumulative stake, or it's the one with the
Most stake owned at a particular point.

It can't simultaneously be both.

If you're talking about cumulative stake, then
a 51% attack could simply pass coins
Back and forth to himself.

And if it's about total stake as a point in time,
Then he wins with 51% anyway.

I would love to be wrong, but I don't think
There is any magic bullet here.