The two excuses for waiting are weak. Excuse #1 is catching all the Slaughterhouse 9 members. The Slaughterhouse 9 lacks Strangers. They are hauling around Crawler! I will be severely disappointed if Survey can't pinpoint their location with real time updates by tomorrow.
Going to slightly disagree here. S9 dealt with Nice Guy. His power was to literally not to seem to be a threat to someone.
"He just stole my sandwich, what a Nice Guy!"
"He just ran me over with a dump truck, what a Nice Guy!"
He just decided to kill everyone living with me, what a Nice Guy!"
Then do remember a few things about Jack Slash.
He wants to be in control.
His power is literally the 'Communication/Broadcast' Shard. The Shard/Agent/Power that let Entities talk to one another. Jacks long rang slashing is 'Communicating' the blade edge to a distant location.
Jack's power is also able to pick up on shards using their power. And even when Parahumans make plans to attack him, his shard picks up on this from the parahumans shards that planned to attack him. Thus, his seemingly ability to avoid being beaten or trapped. It isn't precog, but more he knows subconsciously what other parahumans are planning. This 'intuition' lets him avoid a lot of dangers.
Hence why Joe needs to keep his actions from Imp/Lethe. As she has an actual shard connected to the Network, they use this to share DATA and decide power interactions, Lethe knowing would have her power know. Her power would be sharing this data about conflict to the network. 'Broadcast', Jack shard/power would get this data, resulting in Jack having the intuition to avoid Brockton Bay.
Do remember that the Shards/Agents/Powers are all a part of one of two networks. Further, the Shards are hardwired to promote Conflict, via subtle alteration of brain chemicals.
(Amy with her 'Queen Shaper' Biokinetic shard was constantly depressed and stressed, because she refused to use her power beyond healing. Her shard wanted new DATA. It wanted her to make things. It probably wouldn't care at first if she had made newly colored plants, or a fusion or plants that did super healing, but it would always push the envelope when she stopped giving it new data.)
Pretty much it doesn't matter what power used, Jack would be 'aware' that something was going to happen. Now could he avoid it? Possibly. He still has to work with the limits of his body (Enhaced by bonesaw of course) and his 'known' power of knife projection. He also isn't aware that he has this power. It's all background stuff to him. He honestly probably thinks he was amazing instincts or something.
So, Joe sending out Lethe simply wouldn't work.
Geeze, I went far with this one. Sorry if this came off rude or anything, but
@LordRoustabout is sticking to canon with power interactions mostly. While I do disagree on letting them get to Brockton Bay, I also understand.
To me, Joe has NO responsibility to really anyone. Save his team and sort of the Undersiders. Yes, we want Joe to be the big hero and curb stomp the S9 with 0 to little collateral damage.
But Earth Bet, in particular its governments and the organizations dealing with capes, are super-uber paranoid. Afterall, just look at Nilbog. If he ever left his city, there isn't much that could stop him.
Ape In Iron not only has a massively fast build up time for a Tinker, he, or his 'Team' launched Lung into space via FTL Ram. To consider, the WW2 atomic bombs dropped by the USA, one of them was 18 kilotons. FTL, would be a crapton more energy. Joe is honestly trying to limit the amount of worries he causes by keeping his true level of power hidden. Afterall, if he went willy-nilly and did similar things to others who pissed him off, the American gov would have no choice but to try and force his compliance. It wouldn't end well, and Joe isn't trying to cause such problems for them.
By showing restraint, by not 'nuking' his opposition, when his level of power does eventually come out, while there will be people wanting to somehow get him under their thumbs (Cauldron), his past actions of not going over the top with power will help his position in the public eye.
Yes, this is the dirty side of power-politics. You can be super scary strong and carry a big stick. But if you want to work with people, which Joe knows he might need to in the future, you got to try to keep them from being willing to dive into a volcano or launch nukes at you to work with them.
Sorry, but Joe isn't a self-insert of you or I. I'd love to see a curb stomp fic based off of Joe, where he has no care at all. But this fic isn't it.