An extra coal storage space in locomotives marked with a Tank Engine section in the JSON. This extra space would behave like a tender, automatically refilling the firebox. There would be a similar setup for water as well, feeding water into the boiler like a tender would. This would allow for much more realistic-behaving tank engines, as currently they run out of coal and water much too quickly compared to how they would IRL.

Just going to bump this because with the increasing number of Garratts and tank engines, I think we should address this soon

Closing as dupe of #1200