The design was not unique. I remember Dutch and Polish designers tried similar prototypes with nose and tail propellers.
Rear engine in all tail-pusher designs had severe cooling problems, therefore it was not interchangeable with nose engine. Also, handling problems at takeoff and landing were severe (cannot takeoff/land at high angle of attack without tail propeller striking ground, therefore increasing stall speed near ground). Long driveshaft of rear propeller of Do. 335 did not solve the rear engine cooling problem adequately.
Both problem of cooling and landing become more severe as engines were upgraded (resulting in more waste heat and larger diameter propeller (increasing only number of propeller blades is sub-optimal)). Therefore, even if developed earlier, Do.335 will be disliked in army, plus development will constantly lag beyond competing designs with similar funding for R&D, therefore Do.335 would be eventually phased out during war in favour of more easily upgrade-able designs.
In other words, early P.335 would be deviation of development in opposite direction from Bf.109->Fw.190 direction of development. P.335 will be very efficient as fighter, but operational readiness and deploy-ability will be awful.
P.S. I can image similar design with collective-pitch heads (similar to helicopters) at nose and tail propellers. It can takeoff/land as STOL aircraft, reducing the handling problems, but the design is insanely complex, even by modern standards.
P.P.S. Moving engines above center of mass (to reduce handling problems of tail-pusher designs) is unacceptable for military aircraft. Guarantees sudden stall if engines are damaged.