Theoretical No Sparge Technique

[adm]

Just thinking a bit too much about brewing at the moment, and I dreamt up a potential brewing technique that I'd value people's opinions on (there's probably very good reasons not to do it this way)


Equipment Needed (10G example):
100L mash tun, with built in mash mixer and false bottom (could be a big NO Thermobox with a wiper motor through the lid driving a paddle)
Pump
HERMS/RIMS heater (or temp controlled mash tun) and return manifold

Concept: (10G example)
Put all water needed for entire brew into mash tun at strike temp, mash in all grain (for example, 11Kg of grain, and 73L of water to give a water/grain ratio of approx 6.6:1)
Turn on mixer and mix mash slowly for one hour. Use RIMS/HERMS to keep temp constant, or step as appropriate
Turn off mixer, recirculate wort through RIMS/HERMS to clarify wort
Pump out to boiler and boil as normal.

So the idea would be similar to batch sparging, but with all the water in at once and the mash agitated to make sure the maximum amount of conversion occured. The grains would be being washed in the wort during conversion, so the wort should all be at exactly the same gravity. Once the wort was all run off, there would be no need to sparge and the total amount of wort required would end up in the kettle from a single batch. It seems to me that if you also had a way to directly control the mash tun temperature, then you could do away completely with the HLT and RIMS/HERMS heater too. For example, a PID controlled circular industrial silicone heat mat could be attached to the bottom of the mash tun and directly heat the mash liquor in the tun without potentially scorching the wort like a kettle element

It probably wouldn't be the most efficient method, but would be more efficient than a typical "no sparge" approach.

The main problem I can see (apart from the equipment needed) would be the water/grain ratio. Is there a certain point that the enzyme reaction becomes less efficient. I've seen people mention thin rations like 4:1 and above, but never as far as 6 or 7:1 - is there a chemical reason for this?