If you did write your own firmware, any new firmware that Dish would bring to the receivers may override it. If you used a PC PVR then one could make their own software customized the way that they want it.
Yeah - the problem is that when E* makes satellite system-level changes, it can require firmware changes that would most likely not be usable with whatever we did.
And, of course, it'd be illegal for us to do this anyway - the DMCA, ya know.