I personally tried this on my RX7 (which I no longer own). The SMA/BNC connector was the problem. Performance was only marginally better than the supplied whip. I haven't any knowledge of ICOM replacing it.
If your looking for a better ICOM receiver, I can only recommend the R20. I have owned all the ICOM range and its my considered opinion that the R20 is the best. I use mine predominantly as base station and it handles outdoor antennas such as discone or verticals with no overloads except perhaps my local Fire Station which is less than a mile from me. I have rigged it with a temporary long wire as well for SW monitoring. One of the R20's benefits is the excellent recorder.