About The Joetsu Line is a major railway line in Japan, owned by the East Japan Railway Company (JR East). It connects Takasaki Station in Gunma Prefecture with Miyauchi Station in Niigata Prefecture, linking the northwestern Kanto region and the Sea of Japan coast of the Chūbu region. The name refers to the old provinces of Kōzuke and Echigo, which the line connects. I am suggesting the full length from Takasaki to Miyauchi totalling 162.6 km (101.03 mi). Rollingstock Main 115-1000 series (Takasaki to Minakami, Minakami to Nagaoka) 211-3000 series (Takasaki to Minakami) E129 series (Minakami to Nagaoka) Freight EF64-1000 Class EH200 Steam D51-498 C61-20 Series 10 passenger cars Series 12 passenger car Trips on these trains can vary greatly for more info see the link below. https://www.jreast.co.jp/multi/en/joyful/slgunma.html Future layers 651-1000 series (Takasaki to Shibukawa) E231-1000 series (Takasaki to Shin-Maebashi) E233-3000 series (Takasaki to Shin-Maebashi) Videos
Realistically this is only going to get built by Union Workshop who still seem to have a lot of work left on their current Tadami line project.
As is likely the case with most of the Japanese routes suggested here, since DTG seems to be allergic to going beyond the USA-UK-Germany-Austria quartet. I definitely think this would be a fun route to play, though! Lots of variety with the stock listed above.
Nice and this needs to consider a Tadami line DMU layer. Otherwise purely electric 1.5kv DC or 20-25kv 50/60hz AC route. The best value is Joetsu & Tadami Lines combined that way you can run a DMU from the Joetsu line to Tadami Line using the Koide connector