In configuration the Wilksch is simple - but the major problem is that is has not been designed for simple production. The 'wrist pin' with a hemi-spherical cup and socket is a nightmare in production terms - and it gives issues in terms of reciprocating weight. A 'clever' idea but one whichhas crippled the engines potential.
The total production of the engine is very modest largely because of this. At the end of the day if really does nothing much better than an O-235 might do with fuel injection and a good ignition system.