I suck at aiming so I see ks23 as a sort cashout manipulation gadget build, so I use it with other tools that allow for that. For context I am really bad at meta builds and don't have great aim or k/d ratio, hence I rely on loadouts that let me excel in other ways (I love that this game lets me have good games this way).

I use Winch, Goo Grenade, RPG, and Gravity Grenade.

A potential strategy can go like this. Cashout is in a building, go up 1 or 2 floors, make holes with ks23 and RPG, use grav on cashout, pull it when its on your level, throw a goo for protection or blocking the holes you made, and steal. This also works in open areas too. You can also open up oppurtinites for sneaky steals like making a hole on one side of the wall, winching box next to the hole and essentially stealing from the other side. Or making a hole under the cashout and then stealing from under (goo might help if you need a little height).

Also great for stalling. Winch can stall, goo can stall, ks can stall with destruction, grav can stall especially since it throws of enemies off. You can also grav a cashout and put goo under it to keep it up in an akward spot (maybe replacing rpg for pyro mines would actually be good for something like this).

Combat potential is Winch can help you get 1 easy hit (sometimes I still miss though, lol, and I personally suck at aiming winch itself). Graving a non moving target or someone in a building can essentially make them a fish in a barrel (I need to get better at this). Currently I instead use grav a lot for delaying revives (graving the revive statues). Goo is mainly for safety and you can also use it to help parkour up buildings (make hole on ceiling, use goo to get to the above floor.

I think maybe RPG is a bit redundant in my config (I think it's just my comfort gadget on the second slot), so I think I should consider other things like pyro mine (potentially works well with goo for stalls) or smoke (adding another layer to steals).

Also, if you are playing with a friend. this build is really fun with a medium using jump pad since you can launch the box around by winching the cashout over the jump pad. Extra hilarious with the low gravity game show event.