I like the original PD. The system has alot of similarities to ICON to be honest. But they only ever published 2 adventures and one of those came with a GM screen if I recall. I think in all honesty FASA would be a good choice for you. There is an abundance of adventures and they are all set in the TOS era. The rules are simple and strightforeward. Any racial abilities you want to throw in can be simple role playing aspects or simple bonuses to a skill. It would get my vote. The only downside is starship combat. And they are available as pdf's in a number of places.
The simulator is fun as a tactical game but it is hazardous to PC health if used for the rpg. So you would have to come up with something on your own which is fine as if you are trying to recreate the show it's more of a storytelling aspect than agame mechanic I found. The CODA starship combat is the best of the bunch but you'd have to retrofit it onto the FASA system somehow.
I was REALLY looking foreward to D6 PD but that appears to be vaporware to be honest.
Ok, that's my take on things...
Duct tape is like The Force. It has a light side, a dark side, and it holds the universe together.
- Carl Zwanzig