I suspect they won't want to do that because it'll result in another night rating badly and, as you've said yourself, harm Coronation Street which isn't what they would want to do with their flagship scripted show.
Say for example, ITV moves that Friday 8.30pm episode to Tuesday 8pm. It will result in a new 'FlopZone' on Fridays between 8-10pm and Corrie wouldn't rate as well up against Holby City. Basically the overall situation would be even worse for ITV1 than it is at the moment if they did that.
One thing that is blatantly clear about Tuesday nights at the moment is that the Grimefighter repeats should be pulled from the 7.30pm slot because it's been rating appaullingly and will have most likely had a negative knock-on effect on the 8pm programme. A decent programme in that slot is capable of about 3m (as we've seen with Children's Hospital earlier this year) or if ITV don't want to spend cash, then surely repeating Countrywise or Youve Been Framed there would be better.