Personally, I haven't missed Aliona one bit from this series (I've never made secret I thought she was terrible with Matt, and extremely lucky Harry had the pre-show support he did or they would have got nowhere near the finals with her choreography!) and would be glad to see her not return in favour of Iveta next year;
My biggest disappointment this series has to be Ola! I understand the issues she had with her mother but the Tango/Cha Cha choreography, knowing Sid could dance (Waltz and Salsa), really weren't good! With Robbie, she played so well to his strengths and by his elimination he was massively improved, but with Sid, it seemed like her heart wasn't in it anymore. I hope this was just a blip due to her personal life, and pending her return next series, she can sparkle like she has done before.
I like Erin greatly! I think her stuff with Austin proved how good she is, and hasn't been given anywhere near a shot since, maybe since Anton got his "quirky" character in series 8 and they want more pro dances from them both, but I loved Erin's choreography, thought she did an admirable job with Richard, and would like to see a bit more of her and Anton, if they must go, let it be with a bang and not a whimper considering their longevity. Give them a shot next series, then Anton as host and Erin as judge would be acceptable.