I'd imagine just XORin CSPRNG and HWRNG would solve most of those issues. Even if HWRNG would have problems (say some interference would make it generate much l

I'd imagine just XORin CSPRNG and HWRNG would solve most of those issues. Even if HWRNG would have problems (say some interference would make it generate much less entropy), attacker can't devise CSPRNG state (even if it was vulnerable) because there is no way to "un-XOR" the output. Also for OTP nonuniform distribution would "only" cause numbers on average to have less entropy and that could be corrected by just having them be a bit longer.