Happy New Year!
Your question as to "What has changed in intrinsic electron structure?" unfortunately I don't have a definitive answer for. That answer, if it could be varified by experiment, would probably be Nobel material. But we can always ponder and study.
A real short (cheat) answer, from an engineering prospective, might be "increase the potential difference [add HV pulses] within the system." This appears to what has been done in Ruslan's and others early (2015) devices.
Over the years my leaning has been towards thinking that Dirac's work in the 1930's is more believable, to me at least, and holds the most promise in describing a viable electron structure and interaction.
One long term project I would like to complete someday is integrating the Dirac and Maxwell equations such that modern CAE software (Comsol Multiphysics in particular) had the capability to work in both positive and negative energies (Dirac). There is light however, since I recently read a paper where apparently this has been accomplished.
There are several papers attached relating to Dirac and one that describes a late 1990's project called Genesis. A long while back but it did strike my interest. Also, I am actively working on Comsol analysis of coils and high voltage interaction. So far so good but still a long way to go!