FM3 special mode is a very useful technique for making more interesting sounding instruments or simulating up to 4 channels at the same time. However, it will also be more difficult to program this effectively, as to take full advantage of the features you essentially need 4 trackers with control over TL and frequency of each operator. Also, there will be some issues to be considered with SFX, like should 1 SFX channel override effectively 4 channels? Should SFX be able to use FM3 special mode?
FM3 special mode is a very useful technique for making more interesting sounding instruments or simulating up to 4 channels at the same time. However, it will also be more difficult to program this effectively, as to take full advantage of the features you essentially need 4 trackers with control over TL and frequency of each operator. Also, there will be some issues to be considered with SFX, like should 1 SFX channel override effectively 4 channels? Should SFX be able to use FM3 special mode?