As you described, I would go with a water/glycol reservoir that constantly circulates through the jacket. The reservoir could have a 2 stage controller running a reef chiller and a submersible heater.
The current models for sale include stainless base heating elements.
http://brewha.co/products/ulwd-electric-element
I still plan to keep my existing large mash tun for high gravity 10 gallon batches 40-55# of grain for a 10 gallon batch.
I usually squeeze out excess moisture and freeze a few cups. When i'm ready to make bread or cookies I let it thaw for a few hours, run it through the food processor and mix it into my dough or batter.