Would love to see propelling nozzles that fighter jets have on their engines incorporated into IF. For those that don’t know these are adjustable area nozzles that expand or contract at different thrust for a jet fighter. During lower speed acceleration the nozzle(s) lose area to control the exiting gas pressure . At higher speed and during the use of afterburners the nozzles expand due to a greater area needed to maintain the constant pressure of gas exiting.
Here is a video of a static afterburner test of a J79 jet engine. At the 2:08 mark you can see the flex of the nozzle. https://youtu.be/qZKKeg7lOr8
For more info on propelling nozzles check out this link https://en.wikipedia.org/wiki/Propelling_nozzle?wprov=sfsi1