As a more serious answer, I suspect that it'll all depend on how long Moffat is sticking around for, and indeed whether we're getting full series or not and when.
There's talk of 2016 being a 'Specials' year. I really hope this isn't true, and if it is then not for the reasons suggested. But at any rate, I don't think Moffat will have more than two more years in him. I don't see him having more than a single more series in him. Even if he has, it's high time to shake things up and it'll be an interesting first for NuWho to deal with a Doctor under two showrunners... if Capaldi is still hoping to stay on of course. I don't feel the showrunner can claim ownership over specific Doctor's. With all this in mind, with Moffat closer to leaving than joining, I do wonder whether an all new companion is worth it. A returning character would allow him to focus on the storytelling in his final series, rather than having to flesh out a main character from scratch all over again. A character like Osgood is a prime candidate for that, and I wouldn't mind seeing her brought on board for a series or two. It'd be a bit like how Donna came back, and that sense of familiarity led to a brilliant series (in my opinion of course). I also like to have a bit of overlap between companions, even if its minimal - all the current companions have met each other to a couple of degrees... (Rose met Martha and Donna, appeared alongside Clara sort of. Martha met Rose and Donna. Donna met Rose, Martha, and River. River met Amy, Rory and Clara. Amy and Rory met Clara in the form of Oswin) and Osgood would fit that bill nicely having already met Clara.
If I was to have a bit more fun with the options, and just go for people I'd like to see in a companion role I'm going with the name I've gone with for absolutely ages as I love her - Gillian Anderson. It'd be great to have two older actors lead the show for a while, though she's a good decade younger than Capaldi still. I'd have to accept that she's not Dana Scully and the ginger hair will probably still be out... but I can live with that
Another I would like in the role of companion is Lucy Brown (who played Claudia Brown in Primeval). I also wouldn't mind (in addition to, or instead of the above) a younger male companion as well - as much as I don't like it, Sherlock has proved they can have a show with two male leads and make it accessible. Maybe someone new or someone familiar (the cyber guy from Time Heist wasn't too bad, as the few younger male characters seem to go) ... but definitely a change from 'British young female' which we've had in excess for years now.