If you want a wildly different format with alien captains and leading Ensigns and liberally-minded casting then just make a completely new franchise.
Now come on casting as not been that bad. Especially compared to other Scifi shows. Minorities (talking humans) do actually do stuff in Trek.
Battlestar: One minority of note and that character was orginally a black male.
Terra Nova: All the minorities who do anything are female, impossible to find a male who does something that matters
Stargate Universe: Two Asian Females and One Black Male, they got some decent stuff so pass.
Falling Skies: Minority Female love interest, black guy dies first trope in full effect, black male and asian male barely get lines.
So I protest the notion that Trek is not liberal in casting. Its easily in the Top 90% of SciFi related shows. Could it do better yes but so could all entertainment.