For common people like us it can actually be a big headache
to imagine & estimate a new jet in 2D, unless we know how to use 3D CAD S/w.
Most 3D artists also make models w/o thinking too much themselves.
Let's take F-22 as foundation reference.
If we wan't a better TE jet as per 6gen features of more capacity of weapons, fuel, new components, then it'll be bigger. So if the size/volume/weight is more & if same or more dry/wet ATWR (Airframe Thrust to Weight Ratio) needs to be maintained, then
more airframe weight -> more thrust -> more air -> more area of intake, duct & inlet.
For idea, F-22's F119 Vs F-35's F-135 engines: 100cm Vs 109cm inlet dia., 116/128 KN Vs 156/191 KN dry/wet thrust. 9% more inlet dia., almost 19% more area, 10.3% more dry thrust, 22.4% more wet thrust.
There is no fixed formula b/w area of intake/duct/inlet & thrust, let's assume 1:1 ratio in increase for easy understanding. So if we fit F-22 with a bigger & 33% better engine of 156*1.33= 207.5 KN, the challenges are -
- increase air flow by 33%, means increase area of intake, duct & inlet by 33%. Inlet diameter increases by square-root(1.33) times or 15.32%.
- increase payload & range, means lengthen the jet.
- restrict airframe volume to 133%.
- restrict airframe height to that of F-22 if possible.
If the airframe expands only in width & height then it is easy to estimate.
If the airframe expands in all 3 XYZ axis in same ratio then also it is easy to estimate.
But if all 3 axis have different ratios then we have to be careful not to eceed new volume/weight.
Option 1 - stretch the airframe length only by 33%, which will need tandem IWB for extra AAMs.
Option 2 - stretch the airframe width only by 33%, which can adjust 4 more AAMs easily.
Option 3 - stretch both airframe width & length by ratio such that X*Y=1.33, like 1.1*1.2 or 10% X 20%.
Exploring option-1 1st, the fuselage width remains same, area of intake, duct & engine increased, again there are 3 sub-options:
1A - expand area in width & height by 15.32%, engine can be pushed down, but intake slightly portrudes down & out, duct above IWB is manageable.
1B - expand area in height only by 33%, engine can be pushed down, but intake portrudes down more & duct above IWB produces bump.
1C - expand area in width only by 33%, engine is pushed down, intake portrudes out sideways but manageable, duct above IWB is manageable.
I don't have 3D CAD S/w, so I put the above options 3 sub-options in approximate cross section diagrams of F-22:
So we see that increased size/volume of 1 or some components or system affects other parts & entire airframe.
The engine power, size, weight is dictating design of stealth jet if same ATWR has to be maintained.
So the F-47 is child of X-36, YF-23 or Bird of prey? 
