I think any series and parallel configuration is possible but, if we expand too much the number of engines we find two problems, first space, for besides the engines each carry a driver and engine cooling for each and every driver, the motors are oil-cooled everyone needs a flow of 12 liters / minute, drivers are cooled glycol, two different circuits, one engine and one for the drivers, the second problem would be the batteries, finding space and cooling if necessary, if we use a voltage of 400V each engine provides 120hp highs, and if we use 700V each motor generates a maximum of 221hp, so if we use 2 sets of 3 motors have 400 volt 720 hp highs, and 700voltios have 1326 hp
If we used 12 engines with 400volts - 1440hp and with 700 volts 2652hp, we must also take into consideration, both with 6 engine torque entire system exceeds 2000nm, with 12 the maximum engine torque 4320 Nm, for so the transmission should hold at least 40% more and I don't know a transmission that hold all that torque, we must also consider the transmission ratio to achieve 350km / h, the maximum Rpms of the electric motor is 7500. Then need a several automatic transmission ratios that support all the maximum drive torque or a multiplier similar to that used by Toyota in hybrids would also be desirable at least 3 types of programming engines 2 motor city, Eco mode, Normal mode 4 engines, road, Sport mode 6 engines work and can be used as motors or generators which are not used at that time.