I wouldn't want them to hire someone just on the basis that they are asian, just as I wouldnt want them to specifically go in to an audition session expecting only to hire someone white or someone black, or only someone tall, or short for example, as that kind of thing would probably land them with someone terrible for the part. A companion, just as with a doctor, should only be hired based on their acting ability.
Their was an anecdote from Moffat about hiring Matt Smith as the doctor, where he said something along the lines, that he always thought the doctor should be older and was determined to put it this way in his era, yet with 20 mins of doctor auditions he'd hired the youngest doctor ever. This goes to prove that if your really looking for talent, all that stuff about hiring someone who looks a specific way goes out of the window anyway.
Besides, as far as companions go, they've had old, young, black, white, male, female, English and Scottish all in the space of new who, so for those kind of people who are obsessed with that kind of box ticking they aren't doing too badly anyway. None of those particular traits made them interesting as characters though, their acting ability and characters they were given made them interesting, which is the point I am trying to make.
I don't really see how specifically setting out to make the companion asian would be anything special anyway. People would just look and say 'oh look, there's the new companion' just as they always do and there might be the odd murmur that it was the first time someone asian had done it, but I can't really see it would be much of a bigger deal than it would be if the companion was of any other ethnicity. When Freema was cast as Martha there was the odd acknowledgment that she was the first black companion, but no-one acted as though it was exactly earth shattering news, and people judged whether they liked her based on her character and her ability to play it as they always do and always will. The only way a companion would seem special and different before we've even seen them would be if they were written as from the past or if they were alien. A companion that was another modern day human from an ethnicity we just happened to have not had before would just be a bit like 'so what'