I have no wish to comment on the causes of this accident, only on this comment.
There are plenty Single Engine IFR machines out there
I am not sure that there are that many Single Engine IFR machines - i.e. certificated to Appendix B of Part 27 - out there. If there were, the additional requirement for stability would have a
substantial effect on the safety of operations of singles at night or in a degraded visual cue environment.
It is extremely difficult to meet the (single pilot) stability requirements without augmentation.
Jim