I fly with a fixed wing cordset and an adapter. As an electrical engineer I can assure you the only danger is mechanical
, i.e. the extra connections can come loose.
Since I am only flying heli's right now I simply safety-wired the adapter on to prevent the headset plugs from coming loose. Or you might consider using a piece of Velcro to do the same. I also use a bit of Velcro to manage the extra length of the non-coil fixed wing cord.
The reason I went this way was because I got a very good deal on a used Clarity Aloft headset but they had the fixed wing cordset and I already had an adapter in my desk drawer. One of these days I may splurge on a replacement cordset for the Clarity Aloft, though. BTW I really like them. A lot of folks don't, but if you spend a quality 45 minutes or so bending them into the perfect shape for your head they are extremely comfortable, quiet, and fail-safe (no batteries to fail leaving you without electronic protection). The one downside is they do take a minute to put on.
Finally, no worries about impedances. Almost every civil aviation headset and aircraft out there uses a high impedance microphone configuration and you should be all set.