An interesting discussion, indeed. We welcome more such examples of to and fro. This is what Tech Log is, and should be, all about.
I think my issue is I've heard the assumed temp method referred to as both derate and reduced thrust (each on a different fleets that I've been on), hence for me both aren't suitable for reducing Vmcg.... Thus your post with the 'No, you can't do that'' at the start prompted my thoughts...
It now is clearer.
Flex (assumed temperature is the usual technique adopted) and derate are different animals, although, to the pilot, they appear much the same. It is important to keep in mind that derate is the same as getting a defacto new machine with a smaller engine. The whole certification shebang is re-done, along with things like Vmc and Vmcg. Flex, on the other hand, is the same old engine but just throttled back a bit to reduce the temperatures at the back end. Nothing to stop the pilot pushing up the levers and getting rated thrust, along with the excitement which goes with failures back near the original rated thrust Vmc or Vmcg. You do not want to do that with reduced speeds, lest you die a fiery death.
I used to give these sorts of failures to students on the 737 .. not too sure how accurately the box replicated the real world aircraft but the sim sure gave a good ride and looked pretty realistic to me in the back seat playing on the control panel organ ... certainly sufficient to give me relief that I had never been put to the test on the line ! The real sim value for the student was in the I/F patting the head and rubbing the tummy as I worked them up to 0/0 ops with a failure during the rotation on a min speed schedule, aft CG, etc. and a requirement to track out on the LLZ. They all derived significant training value from the exercise and appreciated it for the good fun it was - all nil hazard training, of course. One upgrade student subsequently had a real deal failure and observed that, compared to the box, it was a walk in the park from the point of view of handling.
The jettisoning system on the BAe146 aircraft has proved very reliable and has 2 methods, a primary and emergency dump for getting rid of the load.
I'm sure. However, as Big Pistons has observed, it remains role equipment and is not subject to the more rigorous reliability assessments relevant to certification.