I agree with Mad. As a player, I'd rather the GM just narrate through my capture, rather than pretend like I have a chance if I really don't. However ... Yes, synthmorphs are basically immune to getting knocked out. They can be incapacitated in other ways, such as frozen in freeze spray, stuck to a giant magnet, or spaced. And they can be hacked. The problem with hacking is either they realize it and can defeat it handily, or they don't realize it until they're hacked, and you may as have just narrated it, because they'll still feel cheated. And like Mad said, there's no real benefit to knocking someone out if you're stealing their ego (excepting flats, of course, but flats aren't synthmorphs). Just kill them and pull the stacks. It's ultimately simpler.

There is some benefit to knocking people out, as you can then sell their valuable morph. Also, for those morphs that are vulnerable to it , very often knocking them out is even easier than killing them, and less messy. Biomorphs are incredibly vulnerable. Freeze spray is a good idea if all you want to do is incapacitate, but if your goal is taking their ego you'll still need to hack them or destroy them. You may have access to a puppet sock if you incapacitate the morph... but all the ego needs to do in that case is ego-cast, which is simple if you are a synth. Surround them with a faraday cage first? Eh, it's too unreliable. Just kill them fast and use lots of firepower so they don't have time to call for help or egocast. Taking down synthmorphs is messy, no matter what.

How about this: What if their backups were stolen instead? So not only they have to escape, they'll have to find out what happened to their other selves.

When you say you're giving the players a fighting chance, albeit lopsided, can they actually win? What happens if, say, one of the players escapes but the rest don't? I'm assuming they're not going to be snatched as a group (much simpler and safer to grab people one at a time, after all, especially if they're doing violent grabs), so that's a very real danger. Never underestimate player ingenuity -- if them getting caught is critical to your story, pre-negotiate that outcome with your players. Nothing wrong with a little railroading if you've already talked to your players and made sure they're okay with it, and playing out the kidnapping attempt can give the players far more info about their attackers than they'd get from a narrative summary. I'm assuming you're going with a combat scenario because combat is generally more fun to play out than having your food spiked with a nanotoxin or the like. In that case, location is key. You can't carry weapons everywhere (particularly in the inner system), and if you have to kidnap someone who might otherwise be armed, making sure they've been to one of those places is quite helpful. Don't forget that communications are instantaneous. If your kidnappers aren't jamming mesh communications in their area, the attack is being reported to the authorities as it occurs, complete with footage of the attackers. Most public areas are also monitored at all times, and jamming the local security feeds is going to attract attention, so the kidnappers will need to be working with a good hacker so that the security feeds are getting the footage from some other day (or otherwise edited) for the duration of the kidnapping attempt. Aside from precautions like that, overload grenades are _extremely_ useful if the kidnapping is taking place somewhere that loud and flashy isn't a problem. Twitch, which was mentioned before, is also quite valuable for takedowns -- I ran a very short combat for a group that ended very quickly when one player sent a twitch grenade amid the group of attackers and five of the six failed their resistance rolls, leaving the sixth to be swiftly dealt with by the second player. It was only meant as a low-challenge encounter, but I hadn't realized just _how_ easily they'd deal with it.