@C855B With respect to the lead filling the fuel tank, I am surprised that no one has made a 3d printed mold of the inside of the tank (use thick walls), melted the lead, and poured it into the mold to maximize the fill weight.
I've considered it, but the tungsten cubes + lead solution is super easy for the ST models - the fit is surprisingly efficient, space-wise. Might be worthwhile pursuing on the Atlas SD45s I have on the bench for detailing, but I haven't done any A-B testing to see if there are gains.
Of course, if I did such a thing and made the STL available, you
know someone would come along and attempt the mold on an FDM printer.

I think he will get a better deal buying them with DCC installed than buying the DC loco and then buying separate decoder. I think the cost difference between factory DC and DCC is less than the price of a separate decoder.
No, the ESU E24 LokPilot - provided you can find one! - is $30-35, while the factory differential DC vs DCC/sound is $105. Now what is a possibility is the factory offers an installation service for the LokPilot for $30. That would be worth the bother, and let them fiddle with the (damn) wheel sander detail and coupler boxes!