Firstly, I would suggest keeping Expertise feats (hell, I give them out for free typically).
If you do plan to use bonuses for descriptive play, I would suggest keeping them "bonuses" and not a replacement for a feat a player might want/need.
Secondly, I would set up a clear guideline with your players beforehand about what is expected of them to be "cool". I think you'll find that what some players think is cool is different from others.
I would suggest simply saying something like, "If you describe your attack without using the name of the power in the description."
For example, if I use "magic missile", I could say, "My wizard aims his staff at the two pirates and blue bolts shoot out..." *rattle of dice* "....and hit! slamming into them."
If a newer player is struggling, help them by suggesting they use the "flavor text" of the power as a starting point and modifying it to the situation/targets.
Thirdly, make sure you're providing solid description for your players to riff off of. Set an example by giving excellent descriptions of monster powers (never speak a monster's powers name - instead use the same rule above), but naturally the monsters don't get the +1 bonus. Ask your players thought provoking questions, "When you use magic missile, does the color of the missile change depending on your mood?"
Fourth, apply this to skill checks too.
These added descriptions provide immersion, fictional weight, and memorable scenes that would otherwise be a battlemat and a power sheet. So, I think it's an excellent idea.
For me, those are things I remember about D&D campaigns. Not how much damage I did when I did power X, but when Balthazar did a front flip over a squad of goons and took them out in one swipe.
Good luck.