I imagine that the DTV movies have been somewhat like a prison lately. No one is really being allowed to create anything; they've just been turned into Xerox machines with pre-made graphic novels on the glass.
Timm isn't meant to be someone who faithfully retells another person's story. Timm made a name for himself by doing some really original things (from his revitalization of the Superman rogues to Batman Beyond).
I look forward to what Timm has next; I'm only sorry that he likely won't be breathing new life into DC properties (something Warner hasn't allowed him to do for some time now).