As a gratuitous judgement - is this a case of an aeroplane "designed" by a dilletante rather than an engineer?
The orginal Quickie has a single piston engine driving a prop which gives it both (a) no asymetric thrust case and (b) plenty of propwash over the rudder to give low-speed control authority
This aeroplane appeared to have two small turbojets replacing the piston engine. From what we saw I would guess that:
1) The aircraft needed thrust from both engines to maantain level flight - it could not sustain height on one engine.
2) No enhancement to the rudder to recover the authority lost due to the lack of propwash over the fin/rudder
3) No enhancement to the rudder to ensure sufficient authority to meet an asymetric flight case
As such the whole vehucle was just not airworthy. As an absoolute minimum it would have needed some system to throttle the remaining engine back in the event of one engine failing, so that the ensuing landing was at least straight ahead and under control. But I would have expected to see a much bigger rudder, toe-in on the engines and/or some form of thrust vectoring vane in the engine effluxes to make the whole concept even vaguely airworthy IMHO. My (speculation and gratuitous opinion based on very limited evidence) view is supported by the in-cockpit views which seem to show the pilot pushing right rudder to the stop, but the slip indicator (the string on the canopy) is still showing a huge left side-slip.
As an aeronautical engineer I have always held the view that any twin which can't maintain height on one engine is actually more dangerous than a single, because you get twice the failure rate with no significant failure mitigation.
€0.02 supplied, YMMV etc
PDR