For me that is not such an easy assumption, because even if you own the majority of amount in a darksend mixing process, you can' tell if the other transactions are just one or multiple people.

At least it is a plaussible deniable that you can't know if it was one or more person. Even if you obeserv it for a long time and analyse it like "these addresses are coming up in this block, these in this and so on, than you could conclude, these addresses must be owned by the same person because they come up all together in a timeframe. BUT darksend mixing, doesn't send all your address trough mixing each time a mixing is going on. So your addresses will randomly splitet and an timing analyses would be not working. And its plaussible deniable - just because you could assume it would be the same person, you cant tell for sure. You just can assume.

But perhaps you can write a whitepaper about your idea, that would be very nice, there is also a big bounty if you get that to work.