I hate to be even thinking this way. I have been having problems getting parts to rebuild my pony motor and shipping leed times are killing me for my d6-8u with a dry clutch. my plan is to drill and install a 12-volt starter in the bell housing. I don't have glow plugs non do I plan on putting any in. really just would like to test my clutch job and see how everything else works on the cat once I get the pony back together it will be reinstalled and use for any cold starting / first start of the day. 
I have a good 1200 watt circulating block heater installed in the D318 can one expect to be able to start it without either but being plugin on anything over 32 F 0 C? planing on using 2 group 31 batteries in parallel or one D4 sized group 31 are a lot cheaper it seems right now. I will have to come up with a way to charge them yet . Does this seem like an ok plan going forwards?  has anyone used a new style gear reduction starter to replace the heavy old MT50? 

Lots of D6's and D4's operate on DES  as you describe.
None of those gear reduction starters have RH Helical drive gears and I don't know of any home built versions.
50MT starters are overkill for the D6. They will start fine with either a 40MT or 42MT unit.

i suggest installing a flame starter into the intake manifold. they are cheap and simple and they work great.

bestfarmparts.com/White-Oliver/Glow-Plug...509k5006j7n11jga64i0

here is a 24 volt version

a small pint or smaller reservoir or plumb it into the return line. gravity fed is sufficient.

in this vid uses the pressure from the fuel filter to supply the thermostart. since it can't gravity feed you need to be able to estimate the glow time for ignition before cranking.

yes the heat from the coil opens a little valve allowing the diesel to drip onto the hot coil and ignite. the rush of air will eventually cool the coil and stop the flow or just stop the current. i have one on my new holland tractor and on the case skid steer cummins engine. both factory set ups using the return line. i have seen them on older case backhoe that used a little reservoir. a switch or button to send current to the plug.

thanks but I don't think I go that route as it's 24V but might keep that in mind for my log skidder as it already has a thread in glowplugs in the intake. so it would be an easy switch.