Craig is my favourite judge out of the current ones, so he can stay.
It would be great to see either Karen Hardy or Erin Boag there because they know their stuff, bring the ballroom knowledge (to counteract Craig's theatrical background) and are both firm but fair. Having seen them both on Choreography Corner, I don't think either of them would have their favourites (and non favourites) colouring their judgement, unlike Shirley 
Brenda and JJ might be too arsy and confrontational for their own good, but until you see them in that position, it's hard to tell. I haven't seen Brenda judging in Australia. They've both burned their bridges with Strictly anyway 
I didn't watch when Arlene was a judge. Wasn't she quite strict? Although, didn't she have her favourites she used to swoon over aswell (Mark Ramprakash)? 
Ian Waite might have been quite good, again - good knowledge. But he's probably more suited to ITT these days.
Talking of how many couples in the final, wasn't there only two the year Ola Chops won with Chris Hollins vs Natalie Lowe and Ricky Whittle?
Other finals have been 3 couples, with one being eliminated half way through, for example, JJ and Pamela Stephenson going out, leaving Matt and Aliona vs Artem and Kara. They used to dance more dances in the final than they do now, iirc.