I have found in my experience with this mountain of man and machine that there are three ways to really use him, and not all of them are truly effective.
1 - Karchev Theme Force "The Iron Curtain" aka "The Fluffy Trap"
Karchev is an excellent briking caster. This is shown when you use him in a brick against something which is susceptable to it like another brick. The problem with Bricking Karchev though is that he is very open to being picked apart by anythign that can either outmanuever him or just plain outnumber him. dont het me wrong. Karchev's theme is fun to play at the casual level. In a tournament though, prepare for some throrough beatings if this is your go-to list.
2 - All Jacks all the time
This takes his theme force, flings out the support elements, and pumps the number of warjacks oup on steroids. Ideally this is run with 9 Berserkers and a War Dog. literally you are simply eschewing tow, using arcantric turbine to gain a focus, and upkeeping sidearms all day for the bosted def and no knock down. Its not highly efective but ut does have an awkward suicide bomber trick to take care of swarms of infantry and still leave you a ton of operational warjacks.
3 - Karchev Gunboat, Karchev with Guns and Support
This is probably the most balanced way to use Karchev. Basically you take Karchev with 2 or 3 shooty jacks that he tows around and lets them constantly gain the aiming bonus, which on a Khador Jack gives them a decent starting statline, and on Black Ivan makes him pretty good at shooting stuff. I prefer Black Ivan and Behemoth for his two towed elements as I get 3 bombards and if I need one of them to crack armor open, they can. usually this can be supported by Widowmakers, Winterguard Infantry, or whatever other support may be needed.
I knwo there is ore to this man in the machine and to how to play him. to go into everything I have learned about Karchev woudl require writing an entire book unto itself for those insights and tactical mistakes which have allowed me to pearn what to do with him and what not to do.
So until next time
CJ out