Currently spool time only depends on the type of cycle.
To make engine performance more realistic and making these highly efficient engines more useful on small crafts, the engine spool time should also be affected by engine size.
Small engine generally has components with little inertia therefore quick throttle respond.
Big engine carries big and heavy moving parts, also the space in fuel line / combustor would be huge, taking more time for exhaust gas to reach the nozzle, that means big engine should take considerable time to keep up with throttle.
Although jet engines were once overlooked and only had one type, they have taken the lead here😒