They could offer him £50K/week, with a signing fee of £4.5M for a 3 year deal. That would nearly equal his current deal and not break the wage cap. And it would be cheaper than trying to get a replacement of sufficient quality IMO.
Interesting thought/suggestion.
If the club do offer Coloccini a new contract, it will be highly incentivised. There's no way Ashley will offer him £80k a week again.