Sorry, but NO.
Sparse storage does not applly to symbolic matrices. Even if it did, this would virtually not help you to speed things up by more then a fraction of a millisecond. The computation bottleneck with symbolic problems is a huge one, but it comes down to the huge complexity of the terms that you generate. And that is true even for small matrices, where sparse storage would be a complete waste of time. In fact, trying to use sparse here, even if it was possible, would actually slow things down if anything.
So sorry, but no. Sparse would be a waste of effort.