I also use MMTTY, but just for the "tuning cross" thing to help me tune in signals. But, I purchased MixW, and use that, since 1) it does a slightly better job of decoding RTTY under adverse conditions, 2) it runs all sorts of other modes, including packet, MFSK and Hellschreiber. But, integration of MMTTY would go a long way towards keeping DX4WIN in the mainstream - it works fine for casual RTTY.
It should come, probably, in version 7.0, while 6.4 will fix the accumulated problems we now face. Right? My latest problem came yesterday in the June VHF contest. Although I disabled my HF radio, since my VHF radio is not connected to DX4WIN, every time a spot came in it reset my mode and band info from SSB or CW, 6 or 2 meters, to whatever the latest spot was. Very inconvenient. John, K2CIB