Strikes me that it might just been more useful to make her a proper telepath. Have any of the writers discussed why they didn't just do that?
The Mirrorball Man wrote:
I may be wrong, but I always thought that Gene Roddenberry came up with Deanna Troi, and he, not being a very experienced television writer, didn't realize that her powers were a nightmare to write for convincingly
I remember reading some quotes from Gene around the beginning of the series explaining how it would be hard to make a full telepath work: a character who's constantly bombarded with everyone's thoughts, who sees their companions say one thing and think another, etc. They'd turn into a quivering neurotic in short order. This is supposedly the reason Deanna was made just an empath.
Of course, that doesn't explain why Lwaxana Troi had no problem with it.
I think those quotes are in an old fanzine article. I'll have to go home and dig it out.