Hola Adam -
xxx
A lot of data and information about design of engines so far presented here.
Sure there are ways to improve on design. But some are not.
Look at the progress of the jet engines for the last 60 years.
xxx
From the centrifugal flow compressors (not so efficient) to the axial flow...
Using afterburners (relight) designs...
From single spool turbojet engines into the bypass and fan engines...
Design of fans on compressor section, or aft-fan (CF700/CJ805-23) on turbine stages.
And finally into high bypass turbofans, all that to increase improved mass acceleration.
xxx
Using SFC comparisons (pardon my advanced "Alzheimer's"), I remember -
JT3C (J-57) which had some SFC of about .75 (early 707/DC8s)...
Fitting a forward fan (JT3D), it reduced the SFC down to .53 (later 707/DC8s).
There was the JT8D (727 and old 737s) with a SFC of .58 - Essentially a bypass design.
xxx
Then came the JT9D class engines (52,000 thrust) reducing SFC to .38...
If I recall - JT9D-7Q fan thrust produces 41,000 lbs of the thrust.
The core of the engine only contributes to 11,000 lbs of thrust.
xxx
Fan blade design, variable inlet guide vanes, variable stator blades are used as combination.
I recall the J-79 (CJ805) turbojet having 15 stages of variable stator blades.
And inlet designs to reduce inlet speeds below supersonic.
xxx
What is next... Tell me. I only know the past, not the future...?
I am retired, replaced a subscription of Aviation Week by one of Playboy Magazine.
I hope future designs will include sea water as fuel, do not attempt using my wine and beer.
Happy contrails, bottoms up.