Acceleration and stuff are based on "weight" so why not add an option that uses the weight values space age added for rocket logistics?
To balance this out, the rolling stock weight should be reduced to 66.6 for locomotive, 40 for cargo wagon, 66.6 for fluid wagon, and 531 for the artillery wagon (also the rocket launch weights of those respective items).
For reference, the current weight values are
Locomotive (2000-->66.6)
Cargo Wagon (1000-->40)
Fluid Wagon (1000-->66.6)
Artillery Wagon (4000-->531)

Under this system a fully loaded cargo wagon (with stone, coal, iron ore, or copper ore) would be 4040kg (4000+40) -
a 1:2 train goes from 4000-->8146.6
a 1:4 train goes from 6000-->12226.6
a 1:2 artillery train from 10000-->1128.6 (empty) 10000-->21128.6(full, 200 rounds of artillery = 20k)

This means empty trains will zoooooom while full trains will sloooooow