It is indeed pretty much impossible to emulate the Cell with a Jaguar. There are tasks in which the Cell is faster than the Jaguar. How would you want to do that? I mean, maybe it would be possible with years and years of work and some programming geniuses. I imagine you could offload quite a bit of workload to the GPU, as the Cell is pretty similar in architecture, especially the SPE units. But in the end, it just isn't worth the effort.
Official member of VGC's Nintendo family, approved by the one and only RolStoppable. I feel honored.