Slow cooker

Would it be possible to use a large slow cooker as a vessel for BIAB mashing?
Plus what is the grain to water ration (in metric) for BIAB mashing?

It shouldnt scorch your grain accurate mash temps might be hard though. Cooking temps are probably going to be too high even on low settings. You could try and rig up some temp control. If you pulled it off I think that would make an awesome mash tun for small batches. I use a normal ratio, and batch sparge. If you're not sparging you're probably going to want your full volume of water (mash+sparge). You should do some searches and see what has worked for others though. Ive never tried it.

Normal for me is 1.25 quarts per pound (not metric I know). But Google can convert for you or check out this article http://***********/stories/techniques/article/indices/45-mashing/1115-managing-mash-thickness

If you have a temperature controller, it'd work great. The fancier ones may not work, I've got one that when you plug it in, it waits for you to hit a button. If you have one where you can just turn it on and off, you can hook up a simple temp control and it'll cycle it on and off for you.