Scale mounts that are built into the game engine, like in MOO2. SE4's scale mounts that have been modded in have the awkward problem of requiring the base component size and cost to be very large, so you get "Ion Engine I is 1000 kT and costs 30,000 minerals?!? WTF?!?

" And you also have to go to the trouble of selecting the scale mount from the mount list every time you want to use a scaled component. Instead, how about allowing percentages or multipliers in the Components.txt file, so you could say
Component Name := Ion Engine I
...
Tonnage Size := 10% <- relative to size of hull
Tonnage Structure := 20% <- again relative to size, so for a 100kT hull it has 20 HP
...
Cost Minerals := 300% <- again relative to size of hull, so for a 100kT hull it costs 300 minerals
or, even more flexible but less readable & harder to implement & design a component stats window for

:
ComponentName := Ion Engine I
...
TonnageSize := [Hull.TonnageSize] * 10% <- the Hull object refers to the hull this component is mounted on
Tonnage Structure := [TonnageSize] ^ 2 * 0.1 <- increases as the SQUARE of the size for some reason

a 100kT ship would have a 10 kT / 10 HP engine, a 300kT ship would have a 30 kT / 90 HP engine...
...
CostMinerals := [TonnageSize] ^ 2 * 3 <- there's that square again, remember the "Economies of Scale Mod"?
