Well, they already made it very hard. Their account requires a phone number. You have to use their community app to appeal for an unlock request, and it only works at a certain time on a day. If it didn't work at the first try, you have to wait for 10 days (this part could be different, 7 or 14 don't exactly remember). Also. it never works at your first try anyway. They limited the unlock count per account, 3 per year, then they dropped it to 1 per year. Last time I heard it was impossible to unlock older devices because they shut down their server. So the very restricted version of unlocking appeal only works for HyperOS versions I think, so if you have MIUI it's not possible anymore.