Question: isolate expresion where variables are matrices

Hello,

I'm trying to find the way to manipulate matrix equalities easily and isolate them as variables like if they were simple real variables but keeping the matrix properties.  However, I couldn't find the way to do it efficiently without describing all the parameters of the matrices.  I'd like to keep them as variables rather than perform matrix operations when defining the expressions. I've attached a snapshot which describes my problem much better:pdf_kmaple.pdf.

For instance, I'd like to be able to isolate the expression that defines the state-space when I change the discretization method.  

I'm wondering if there's a generic way I can use to isolate other matrix systems as well.

Thank you very much for your help!

JMarc