There are some very powerful third-party avionics out there. However, it is currently not possible for those developers to port those avionics into the default aircraft cockpits. Here is an example from TDS about their excellent GTN xi package:
http://www.forum.tdssim.com/thread-143.html
There is a fairly awkward way to use these packages to replace the default G1000 systems, but the ability to actually modify the cockpit would further improve these developers’ ability to innovate with avionics.