It would be really creepy if they actually changed strategy and tried something like diplomacy.
That's Dominion turf - and that is what makes the Dominion creepy, that they are not hamfisted and obvious like the Borg or Klingons, or even the Romulans. They are truly a dark version of the Federation, and can use all the Fed tricks against them. So if you want a villain like that, use the Dominion.
The way to make the Borg scary is to stick with their core characteristic - their terrifying and pure simplicity. No trickery or diplomacy, they are straightforward and machine-like. Lose the Borg Queen idea or any whiff of individuality. Think simple, simple, simple.
The Borg need credibility. They have lost their terror because they get defeated too much. There must be an ironclad rule that Starfleet
never defeats them and only rarely even escapes with a bloody nose. Have the Borg win over and over and over again, and they will be scary.
The other ironclad rule: Assimilation is permanent. NO frakking exceptions. EVER! The minute you start rescinding assimilation, it's all over for the Borg. They become jokes.
No ethical Borg. No whiff of them being normal humans. They have lost their humanity (or humanoid-anity) permanently. This is another variation on the no-go-backs rule.
And let them assimilate a beloved main character, for good, no go-backs. Someone like McCoy or Trip. Gotta be a real gut-punch.
So the key here is that the Borg must be used sparingly. You can't have them blowing up the Enterprise more than once (tho I'd let them do it once) or assimilate McCoy, Spock and Chekov just for good measure in one episode.
One thing I always thought they missed out on with the borg was the biological traits of the different races.
Nice idea. How about Vulcan Borg that retain touch-telepathy? And are there un-assimilatable races such as the Changelings or the Medusans? Could Starfleet counter a serious Borg attack via an alliance with the Dominion, which starts churning out Jem'hadar foot soldiers who automatically self-destruct when they biologically detect the beginnings of assimilation? Or just recruit whole starships of Medusans?