To avoid aliasing you need to be able to control which harmonics are present in the signal either using FFT or a Filter. You'll need to be able to do upsampling in good quality which is why filter design is important I'm not talking about biquads, rather FIR filters. If you can process a signal with FFT in C++ and back again, and you can use FIR filters to do oversampling then you should be able to do a WT engine.
Here is a good resource