I would love to see an alien as Captain of the next series, and I thought we need another woman. As for Trill, its a recognisable species without being too alien in appearance (which could put off potential new viewers).
As for the Cardassian on the bridge, I did consider having her and a Bajoran male at conn/ops but thought that might be a little cliché. But as you said, many of the crew could have a bad reaction to her being onboard, so leads to a lot of tension that could be explored and (hopefully) resolved.
The Cardassian would have to be female though, after all the first Klingon and Ferengi in Starfleet were male, so that needs to be balanced out.