I believe there are several ways to make it work, and of course make them optional for whoever wants it:
AI uses better tactics and does better transfers in the harder difficulty compared to the normal one. This one is controversial to me, as that would impose that the normal difficulty has to be programmed to make dumber decisions.
Enable the player to tick on some restrictions for the player (like a nuzlocke challenge in pokemon games). For example, only 1 signing per transfer window, no signings at all, only signings from the country you are in, etc.
Include cheats for the AI -> for example more sugar daddy takeovers in the world, better sponsor deals for AI clubs. Could be anything really, although im opposed to AI cheating in the match itself. Anything to keep the AI competitive in the long run