How to word this to help everyone understand the purpose of the thermostat and the possible drawbacks of installing a lower opening temperature replacement.
The thermostat does not stop fluid flow in the cooling system, it regulates it. The radiator is your water to air heat exchanger, and it's job is to extract heat from the coolant. If the fluid passes through the heat exchanger too rapidly, it can not efficiently shed it's heat through the core into the air. Lowering the thermostat temperature will increase the duty cycle on the radiator, meaning it will see a higher frequency in temperatures rising and falling in normal operation and will have a corresponding loss of time during high loads to cool the fluid.
The only way to combat this is to adjust the fan operating temperatures in the tuning because the 6.0L uses a computer controlled fan clutch. You'll use more power driving the fan and in turn see a small loss of usable power and efficiency in the process. Failing to adjust the fan temperature set points will result in an increased temperature swing in the cooling system under normal operation, and may result in the inability to control temperatures during heavy work loads.
The volume of the stock radiator is large enough that it can fully swap out the fluid volume of the engine with cooled fluids. You can play with the size and efficiency of the radiator to a point with no I'll effect on the cooling system. As long as the volume of coolant is sufficient to "swap out" the hot coolant in the engine and the radiator can cool that fluid off before the thermostat allows the next exchange, the cycle will continue seamlessly. If the radiator is too small or if it end up being increased in capacity to the point that air flow through the core becomes insufficient for proper heat transfer even with the aid of a fan, you can end up with the engine running hot despite your efforts to improve it.
I've been down this road before with C2 Corvettes, 65-68 Mustangs, later model Mustangs and Camaros, and especially in 1980s/1990s 1/2-Ton through 1-Ton pickup trucks where the size of the radiator and/or the available air flow is limited. It is not uncommon even now that the classics are 50 year old vehicles and you'd think the knowledge would be out there, that using 160° and even 185° thermostats make the overheating problems worse, not better. High Flow thermostats ALSO make the problem worse not better. Packaging thicker "high efficiency" "heavy duty" radiators into these vehicles without substantial increases in fan flow makes these problems worse, not better.
Now, as for the cold weather warmup, maybe somebody needs to come up with a way of remote mounting an EGR cooler and diverting the waste heat from the exhaust back into the cooling system for accelerated warmups in cold climates. Regulate the flow of exhaust across the heat exchanger to prevent overheating and flashing the coolant. It sound crazy but wouldn't be all that hard to do. I still think the EGR source and thus the cooler should have been located post-turbo, since the exhaust composition would be essentially the same, and still inert.
The Current Truck (Oct-2013 to Present):
1999 (Early) F-350 Lariat, CCLB, SRW, Black/Tan
7.3L Powerstroke, 4R100, 4x4, 3.73, 37x13.50-18s, '05 Axle Swap, 6" Fabtech lift, GTP38 "D66" turbo upgrade, SCT 4-position chip with custom tuning by me, Straight Piped 4" down pipe through 5" dual stacks, N-Fab full length triple steps, Pro-Tech cab guard and tool box, louvered 5th wheel gate, Hella 500 Fog and Driving lamps, much more to come...
The one I'll miss, (Mar-2009 to Jan-2014):
2000 Excursion XLT 4x4
6.8L V-10, 4R100, 4.30, 285/75-18, 271whp / 388wtq
The one I won't, (Jul-2005 to Sep-2012):
2005 F-350 XLT, CCLB, SRW, 4x4 FX4
6.0L PSD, ZF-6S650, 3.73, 35x12.5-18, 4.5" Lift