PES 5 as base
add all PES 6 modding achievements (new player models, 4k internal graphics, etc.)
expand database to PES 21 size - no need for licenses for all I care it can be another row of Team A, B, C...
international challenge mode with all available national teams so we can have qualifiers for all zones
i guess better attacking ai? otherwise no real gripes with the gameplay
and biggest one, master league
instead of pretending it's a real simulation of football world (it isn't) stick to what worked in PS2 era - PES Points and ability to mix leagues. Except make it customizable as fuck this time around
-number of leagues and divisions so you can go 4 leagues with 3 divisions each or 8 leagues with 2 or 6 with 3, then 2 with 2 and then one with one - whatever! provide some templates for quick start but otherwise allow you to structure your ML as you wish.
-in the same vein you can configure eurocups, maybe even be able to add a third one (intertoto cup anyone?)
-ability to define some constant values like amount of points per wins, promotion, development growth rate (PES 5/6 growth is a bit op but like 80% of that would be amazing) and others
-a better transfer ai but that hasn't been achieved until today. When u play pes 21 and see andy robertson moving from arsenal to real madrid you realize konami just dont transfers.
extra points: master league online except its not some hi-speed mode for sweaty bois but just ability to play the same master league save with multiple people
tl;dr a man can dream 🐑