Ah, I thought you meant him turning into goo was a sign that he'd never been able to regenerate. Like "Time Lords regenerate, gangers return to the ooze."
Well that too. I just think it'd be a far-too-easy way of making new Timelords. I mean, why not make a ganger of River, and then she and the Doctor could happily frolick about after real!River is dead, and regenerate lots more? Heck, then we're back to 'I can use my regeneration energy to get my love back...'