This particular story idea made me giggle. Here’s the thought:
What if, by using the the briefcase Klaus was actually shifted to an alternate timeline when he went to Vietnam. Also, realistically, Klaus has 0% subtlety and is surrounded by people who need something to break up the hurry up and wait. He tells stories about who he is, what he went through, and where he’s from to every single person who asks(including in a weird day a couple of VC who had been captured) and a few that don’t.
This is the timeline that Five brought them back to at the end of S1. They arrive in their childhood bodies two days before Five would have left...only to find that the Umbrella Academy had been under siege by members of the 173rd for two months.
In this timeline the soldiers of the 173rd, half a dozen assorted members of other units, and 5 former Vietcong all remember the soldier they affectionately named ‘Spooky’ and his tales of time travel and the Umbrella Academy. After the first mission by super powered children these soldiers get in contact and effectively go ‘fuck the timeline’.
They obviously don’t want to hurt the kids so that limits how ferociously they can attack the Umbrella Academy. Instead they make it impossible for the kids to be sent on missions or outside training (The first thing a few of them did was blow up the mausoleum). They also make is so Reginald can’t leave to take care of outside business. These soldier have just enough connections in high places that they are to not being arrested and they take a leaf from Spooky’s book. When the new vans arrive they talk about time travel and how that had revealed what was going on in that house. They never quite mention who went back or to when they went back, which prevent the commission from being able to correct the timeline.
I picture there being a rotation of who gets to punch Reginald Hargreeves (Sometimes in Effigy, Sometimes in reality).
During the two months before S1 Hargreeves arrive in the past, the Umbrella Academy does try to get past the soldiers a few times. The first time Reginald tries to send them out, a few of the Ghosts (guess who one of them is) of the 173rd manages to talk to Klaus (and earns the boy eternal gratitude when they chase off nearly all of the screaming ghosts). They tell him they are here to rescue all of the from Reginald and that they are not going to hurt the kids. This makes it so even Luther hesitates in using his power against them.
Four days in Reginald forces Ben outside to release the Horror. No one is more surprised when, instead of tearing the soldier apart, the Horror starts playing Frisbee with the soldiers. (The eldritch tentacle creature knows okay).
By the time S1 Hargreeves arrive the Siege is basically members of the 173rd breaking into the Academy and trying to find the siblings to convince them to leave. Also possibly to find Reginald Hargreeves to punch him in the face.
Queue Five freaking out, because timeline disruption. Klaus being ecstatic, a whole list or reasons starting with Dave and continuing with the blown up mausoleum. Everyone else in the house being slightly confused (Because, What do you mean you served in Vietnam, WHAT do you mean Ghost boyfriend. WHAT THE FUCK DO YOU MEAN tortured by time assassins.) The 173rd cheering because Spooky remembers them. Reginald being punched in the face, this time by Dave (He has had a permanent black eye for two months).
Luther, trying to be better because he does love his siblings he is just really really bad at decision making, invites the entirety of the people who had been laying siege to the Umbrella academy to move in. Luther is so so happy that he is not alone in the big, empty, building like before.
Just shenanigans all around.