I don't know the answer to your question but I thought Bebe Neuwirth's role was terrific and not at all a waste. And in fact, "First Contact" is one of my favorite episodes, in part thanks to her.
If you liked her that's cool; however, I don't really agree. She basically played some no-name horny nerd-alien who appears out of nowhere and wants to jump Riker's bones, and her screen time was about two minutes, at best. It felt like her scene was just shoehorned in, and was unnecessary to the rest of the plot. As the above poster said, a complete waste of her talents.
Although Kelsey Grammer had even less screen time than Bebe Neuwirth, at least he was a dignified Starfleet captain who didn't act like a complete idiot.
IIRC K.G. did Cause and Effect for Scale because he was a huge Trek fan and just wanted to be in an episode. Not much different from Mic Fleetwood playing a holographic Klingon. They just wanted to be a part of Trek.
Fleetwood played an Antedean in the first season. John Tesh played the holographic Klingon.