What I think would be the best overall solution is to have a variety of options when it comes to preserving or otherwise saving your channeler when he is killed in battle. Each choice should be permanent and have its own set of strengths and weaknesses.
1) You clone yourself. These clones share equally in your power, your total power is determined by the combined power of each clone, regardless how far apart they are. When you take power from yourself and imbue it into your empire, the power is taken equally from each clone. When casting global spells, your power is determined by the total strength of all the clones, when fighting in a battle or casting a localized spell the power of the individual clone determines how strong he is in that endeavor. When a clone dies, his magic returns slowly over a given period of time to the others. Reliable but weak.
(if you have 100 magic, and make 3 clones, yourself and each clone will have 25 magic. You still cast global spells as if you had 100 magic, but you and each clone are only at ¼ your full power in individual battles, to clarify. When I say clones, I include the original)
2) You create a successor. In all shapes and forms, this person is a channeler, except that he has no magical abilities until you die. He then becomes you over a short period after your death, and is as powerful and capable as you were at the time of your death. The successor takes a lot of time to train however, and is very vulnerable to assassination, and could possibly even be turned against you. Powerful but possibly unreliable.
3) You cast a spell of reincarnation. This spell takes awhile to cast, and must be completed before you die. Once completed, it will activate upon death and be spent, needing to be recast for your resurrected form. Once triggered there is a small delay for it to complete the resurrection, and the results are not always as expected. You could be brought back as a ridiculously powerful butterfly, with a unique spell called “Swarm of the Monarchs”. Or maybe you get your old body back…it’s a mystery. Reliable, but not always predictable. Only Man (the race not the gender) can use this method.
4) You imbue an item with your soul. When your physical body is destroyed, you do not die, your spirit is still tethered to the world by said item. You gradually make a new body for yourself, and can then once again move about. While in this disembodied form, you can still cast spells but can no longer interact directly with the world, other then to command your empire. If an enemy manages to destroy this item you die forever, though getting it is no easy task. Reliable and powerful but still vulnerable to instant defeat. Only Fallen can use this method.
I think you can see what I’m getting at. Either way there should be some sort of power decrease for using any said method, that way choosing not to protect your channeler from death is a valid choice aswell.