I would like to see:
An awesome salarian - We only ever see salarians in relation to the krogan. I want a salarian completely unrelated, an awesome commando (Spectre?) who does awesome things. Since salarians don't seem to do courtship, he can have a fun personality throughout
Hardnosed turian - Garrus says he "doesn't make a good turian." You know what, maybe that's true. Show me one that is, then
Not-Bimbo Asari - I really don't want an asari (Liara has spoiled the race), but I'm going to say we're going to get one because Shatner. However, I'd like one that isn't just some "Shepard-sama" waifu I'm forced to talk about how wonderful she is. Samara did this. Now give me another non-fetishized aspect of asari culture
Quarian Biotic - I wonder, given how biotics consume more resources than the average person, how someone like the quarians would handle that.
Space Bond and Space f!Indy - For my human companions, I'd like to see a suave spy-type on a mission and an adventurer type who prefers the direct approach. Since there are plenty of femme fatale spies and Bond is freaking awesome, the former is male and the latter is female.
A religious squadmate - Cassandra and Leliana did a good job. Let's extend that to space. This squadmate need not be human. Mordin's wheel of life dialogue was utterly amazing.