Are you planning to convert it to RIMS or Herms? If not, you'd be better off using a cooler to mash in IMO.
I have a keggle but only use it as a HLT and occasionally a BK. I've never mashed in it. Not sure how well it would hold temps and my cooler does a great job of that.
Funny I should come across this thread. I used whole cone hops for the first time last week. At first I put them in a mesh bag, but found I've only created a raft for the hops to ride on top of. I then sanitized a spoon and pushed the hop bag down into my beer only to introduce even more O2. I...