I understand, but this request seems to be very situation-specific, so at this point it doesn't look like adding it will benefit many users, I'm sorry.
While I can think of some situations where cross fading would be nice to suspend, I also think the track tool may help.
I can't think of a case where I would want a track to play with it crossfading only under specific conditions.
If, lets say, I have a block of classical music, The crossfading should be disabled while that block of tracks is running.
A classical piece will never play during a time where I need tight crossfades. So it would be safe to change the file properties so that crossfading is disabled for those files.
That doesn't get you exactly what you want because this assumes that you're only playing a limited selection at the point where crossfading is suspended, but its something.
All that having been said, if you really... and I mean REALLY want this functionality, heres another idea.
Configure radioboss so that edits with the track tool are stored either internally in the database or as files in the folder that contains your audio.
Now, use symbolic links to make a virtual copy of the folder containing your music.
Creating these links doesn't take any space on your drive but lets you have virtual read-only copies.
Finally, load the "files" created by the symbolic links and disable crossfading.
When you call the original file you should get a copy which will crossfade. If you call the sym link, you should get a version that does not crossfade.
Don't worry, windows is cool enough to deal with actual files that exist among symbolic links, so nothing should crash or get corrupted.
Just so you know, I tried this for you... It does work.