
Asymmetric thrust
Thrust asymmetry can mostly be solved with trigonometry: as mentined above, four engine4s firing away from the folded wingtips at a shallow angle providing the upward oomph, with two engines firing at a larger angle from the centreline in order to clear the folded wings and balance the thrust. A single combustion chamber with multiple nozzles would need custom manufacturing and would be extremely difficult to make, especially given weight constraints.
The tricky part will be ensuring simultaneous ignition; this can be addressed by having highly charged supercapacitors for the igniters. They will provide a REALLY high-current pulse which should be enough to fire all 6 igniters within a millisecond or so of each other, especially if the igniters are all wired in parallel (the first igniters burning out will result in even more current through the laggards, triggering near-instantaneous completion of ignition).