Anyways I now have about a week to try out your discoveries

Now to my developments in the past hour or so (and an introduction to what I've done before):
With my hexediting knowledge before, all I did was switch a few values under for example czech_rules.cpp but when you started the thread over at the CM forums, I started looking at EHM with Olly as well (BTW I did find many Push 7D6 commands, all you had to do was make Olly run the program further). Anyways I found out that the codes at that I was editing were actually references to other locations in the exe (I thought that already before but I just couldn't find them). So for example the import restrictions code for the Czech Republic (under czech_rules.cpp) is 30 24 8F 00, which through Olly I found out is actually the offset 00 8F 24 30. There I found a command with a 3 at the end (command in hex is C6 06 03) and the Czech Extraliga has originally a 3 foreigner restriction. I was able to find the corresponding values for all the other leagues as well. However the hex values I found where not the same as the values in the exe at the same offset and so when I changed for CZ the 3 to a 6, the game crashed at the league info screen. It turns out that the exe is probably encoded or something. So long story short, it didn't work and Olly was no more help.
But now with ArtMoney I have found out that at least for import restrictions, it is editable! It's not possible to find it in the search bar and so you have to select the bar "Process" and click on "Memory editor". After that in the bottom left corner, you have to change "Moving in memory block" to "Moving to address" and put in for example 008F2430 for the Czech Republic and change the 03 to whatever you want and it takes immediate effect in game.
It is difficult however to find out which commands mean what so I first have to find them in Olly and only then can I test them through ArtMoney. I'll keep you updated whether I can edit league size as well. Hopefully this means it opens ways to also editing more things such as league schedule, playoff structure and for example adding shootouts to leagues.
BTW How did you come up with ArtMoney?