Originally Posted by Kaboom
Well, he already did purposefully introduce something in the new timeline. He gave Scotty some "help" figuring out his Transwarp Transport equation thingamajig, decades before Scotty would have otherwise worked it out on his own. He should do him another favor, and warn him to never step foot on the Jenolan. XD
Overall, since he's stuck in this "alternate" timeline, to which the Temporal Prime Directive likely doesn't apply much to, he'd probably see fit to warn the Federation about a few of the "big" things that might threaten it or its present and future allies. Like V'Ger, the Whale Probe, the destruction of Praxis, the Borg, the freakin' Nexus, etc... It'd be hard to predict how things would change, but the Federation and humanity might end up better off for it.
As for introducing more advanced technology... Well, Spock didn't exactly bring much of that back WITH him aside from the Jellyfish, which was destroyed. But Starfleet already got itself a nice boost in the wake of the Kelvin incident. Didn't even really need Spock for that one.
I think there's a difference between imparting information in situations that require it (i.e the Transporter equation which was needed to get them back onto the ship, but which is still an iffy technology) and wholesale interference in people's lives - especially since those live may not unfold the same way now.
Scotty may never go near the Jenolen
in this timeline because something might happen over the next decades to alter his life. Therefore there is no immediate need to warn him.
It's that kind of Flash Forward
thing - if you tell someone too much they may change their behaviour and things can go even farther off course than they maybe are meant to.
When it comes to people, Spock would be as well remaining tight-lipped at least until he has knowledge that certain events may come to pass, otherwise it's scaremongering for no reason - 'Hey Jim! Don't launch the Ent-B - you'll die!!', 'Hey Jim, don't sleep with Carol Marcus - she'll have a kid you'll never know and he'll die!'.
The repercussions of such knowledge would not automatically lead to a happier outcome.
Larger thing like V'Ger etc (though most of them are a long way off) he can deal with as they crop up, if he needs to.
For the most part, now that things are settled he should let this timeline unfold in whatever way it does from now on, without trying to influence it too much.
That's just my 2 cents.