Morpher needs to use the exact same mesh for each morph target. you can make copies and move vertices around but you can't change the vertex count or delete faces etc..
It sounds like you might be approaching it in a difficult way anyway. You need to model a mouth into the head and copy the whole head making different expressions for each copy.
Either that or maybe make a seperate lips object that sits infront of the head.
For simple cartoony lip sync the jason osipa technique works great. model four targets wide/narrow and open/closed. make closed the default position.

a little open and some narrow makes an "ooo" sound
wide and closed makes an "eee" sound
Open and wide makes an "aaa" sound etc..

you can make every sound with these four and its easy to animate too.

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