Could I substitute bacon for the pancetta and cream cheese or sour cream for the creme fraiche and still have a great dish?

as it happened, I had no cream when I made the recipe, so used low fat milk (usually I wouldn't, but my daughter has decided we should comply with nutritional guidelines and buy low fat milk). Never have creme fraiche on hand so used sour cream. No pancetta, used bacon and left it out of my son the vegetarian Critic's portion.
Rave reviews from everyone, but I want to try it again with the cream.

I dunno, I have used cream cheese mixed with milk in similar situations... about 1:3 proportions (less crm chs) The cream cheese thickens and gives it a tang that is not so dissimilar to creme fraiche IMHO...

Yes, bacon would be great. And sour cream should work but I would not use cream cheese.