Solver factory cannot be instantiated with dynamic blocks

The solver factory fails to be instantiated with dynamic blocks like BCRSMatrix<BCRSMatrix<...>>. This seems to me that is because that there is not an agreent on what a matrix is... The preconditioners assume that the assembled operators are a matrix and its blocks are either numbers or matrices with the DenseMatrix<...> interface, thus, all of the preconditioners with the exception of Richardson will fail to be instantiated for depth==1.