Except for this part, which sort of negates all the rest:
This plan makes the Son'a look pretty scummy, but perhaps not bad enough to provoke a war with the Federation
But we saw how a supposed friend and supporter of the plan reacted to every step of Rua'fos plan when actually confronted with the truth. Forcibly removing the Ba'ku, stopping Riker, starting the collection before removal of the Ba'ku was complete - the response always was "The Federation didn't agree to this, we lose support, this is wrong, there's gonna be war". Of course followed with "Oh, well, I guess we have to do it anyway", combined with Rua'fo's "What happens in Briar Patch stays in Briar Patch".
Without Data's initial meddling, Rua'fo would have had excellent deniability and control throughout the operation. Especially as regards the holoship. Sure, it was of Federation manufacture - but who do we find aboard it? A Son'a assassin and nobody else! When the Son'a cabal is beamed aboard the holoship, the vessel remains as outside Federation control as ever (locked up, but without any UFP crew, or any signs that there ever was any)... Indeed, the Feds have better control of Rua'fo's own command ship soon enough!
Had the Son'a had "simpler" motivations, i.e. merely a need for the elixir of youth, there's an obvious, simple path they could have taken: tell the UFP that the Ba'ku are mere "interstellarly aware" squatters who can be directly contacted and ordered to leave, free of Prime Directive considerations. Destruction of the Ba'ku lifestyle is an obvious element here, and if the Federation doesn't agree to that with all the facts available to them from the start, the Federation is not likely to agree to that after the fact with all the facts revealed to them, either!