Recruiting Bo is possible even if you are an enemy to the Tech Hunters!
Hey! Just thought I would slip this into the general knowledge of the ever expanding Kenshi Reddit.
If you are an Anti-Slaver, inevitably, you will get into a fight with the United Cities. Unfortunately, your Tech Hunter faction reputation is also at stake when you go to war with UC Cities. Attack a UC city and you will likely get into a fight with Tech Hunter Guards.
I did this before recruiting Bo, who is chilling in Black Scratch. You would assume that someone with such a high bounty with the UC would have made enemies with the Tech Hunters, considering how easily that can happen with the player.
So, what to do to recruit Bo? You can't walk into Black Scratch with a reputation below -30. You will be kill-on-sight. Second reasonable thought would be to disguise yourself. This will get you into the city. Every NPC will still show up as a red hostile when you hover over them, you will not be able to interact with anyone who is a Tech Hunter faction member.
Before you get to this moment, make sure to choose your disguise wisely. If you do not, and enter the bar where Bo is with a full UC disguise on, you will not be able to interact with her either. Everyone in the bar, including Bo, will show up as hostile to you. Luckily this situation is solvable. You need to blow your cover in the UC disguise by taking it off. Leave the bar and take your armour off. Once you do the first nearby guard will attack you, ignore them and run for Bo, who now knows who you are. Interact with her and run out of the city. She already has a high enough athletics that she can outrun the guards, just make sure the guy you brought to do this with also does!
A bit of a ramble, but I did not find any information on this anywhere so decided to post it here for anyone who finds themselves in a similar situation. You can mod in a Tech Hunter Pacifier as well, but this is not needed, UC disguises will work as long as you take the disguise off before entering the bar and can run out of the city fast enough after recruiting Bo! Hope this will help someone!