Nios and the FAA

Has anyone had experience in certifying designs that have a Nios core with the FAA? I work for an aerospace company, and any design that has a microprocessor in it must have its software certified by the FAA per DO178b. The level of certification depends on the safety criticality of the instrument. For example an engine controller would have the highest level (A) and a blinking light would have the lowest (D). Discussions among our software team have came to the conclusion that A-B would be hard to get past the FAA, but some of our low end products may be OK because they are level D. I don't know if it's an FAA attitude, but our regional auditor has a problem with soft cores. I kind of see his point. Soft cores get re-routed every time you make a change (both by synthesis and route). I've seen custom FPGA designs that have components that work until you change another vhdl component. The components that worked, sometimes don't anymore. This is because of race conditions that were design defects. They worked because of a particular route, but when the route is changed.. bam, the race condition is there. I don't know what is needed by the FAA. I would like to see what it would take, because a soft core like the Nios completely eliminates processor obsolecence. If an FPGA is no longer made, just fit it into another device. No software changes! If we make any changes to software, we must re-certify.

Any thoughts?

Rick