You used the word "likely" two times too much. Vague assumptions are not enough to base an attack on.
Many (anon) stakeholders have their PoS private keys in cold storage. Good luck in finding them.
The "crypto-currency" community is small enough of a network let alone the Nxt stakeholder community...sheesh. We are not talking about 6 degrees of separation here but 1-2 degrees to connect most individuals.
15 stakeholders hold over 75% of Nxt:
http://charts.nxt.org/cDistribution.aspxAre you suggesting that these stakeholders are likely not some of the same creators and early investors who know each other?
The reason I use qualifiers is because I am honest about the possibilities and realities of security and there exists a very small probability that those 15 largest stakeholders are complete strangers. I'd be inclined to suggest that over half of the 15 are friends and collaborators. What do you think?