AoE1 had easily moddable ai and per files. I had a lot of fun tweaking the values and trying to make new AIs that can beat the default one. They were also a powerful tool for scenario editors, so I hope the ai and per files or their equivalents in the new version will remain easily moddable.
Age of empires 2 HD edition supported mods, Maybe you might be lucky afterall?
I hope so, or at least a new way to mod the ai, it was one of the things I spent hours on for testing and trying to perfect it, and it would be an amazing thing to keep available 
That being said I really think there are newer and better ways to handle ai then what was done in the age1 per files 
They have said that old scenarios will be compatible with the new version, so I guess that means there will have to be at least some kind of support for the old ai and per files even if they are not used by the default AI anymore.
Quote from Msplus2joe on steam forums:
Third, Age of Empires: Definitive Edition IS a Windows 10 exclusive. Some folks in this thread have pointed out that there’s currently no mod support on the Windows 10 store, and they’re right… While I don’t have anything more to announce right now about this, I want to put some fears to rest by making clear that we absolutely understand how important mods and custom scenarios are to this community, and we have not neglected that as a consideration for this title. Keep an eye on our social channels and AgeofEmpires.com for news in the future.