It appears the new CF6 engines retain the same startup time the PW4000 has despite the GE engine starting much faster in real.

The initial starter crank is fairly good as it is, but the startup following ignition should take about 25 seconds and absolutely no more than 30 seconds to reach a stable idle. In my experience 30 seconds is even pushing it on a ground start which generally is a slower process than a normal start.

The trick is to make the start faster but to not alter the engine response or rpm rate of change/acceleration over 62ish percent N2 because over that you wouldn't want it much faster than it is otherwise it ends up like certain engines on an A320 sim that a certain other developer makes where the engines spool up way too fast.