Myself, starting off at the bottom and working my way up is part of the challenge. It could be too easy to start in the top division and work on it to win everything. It isn't as much of a challenge as starting off at the bottom I think. Now as I have only been playing a few months, I've only played really two teams: UCLA in South America/Venezuela/Segunda Division and Youth U in Australia/Aus_Victoria/Provincial 3rd Division NW. And from my limited exposure to the game, I would say the Youth U game was the harder of the two and actually would be quite a challenge to a lot of people I might guess. Or at least it will drive people as mad as I was when playing, since it is challenging enough and makes you think for sure.
So my current nomination for a very hard starting position would be in the Continent of Australia, the Country of Aus_Victoria, and the Division of either Provincial 3rd Division NW or SE. And here's why I think so.

Of note for Australia/Aus_Victoria, they do have a country wide league cup that all teams can compete in, but to win, you usually have to be part of the top or second top division with a really good team to win. Myself, I've never won in my 18 seasons playing but I'll see if that can change any. And as for winning the Premiership division, I don't know what happens after that, if anything. Additional points are that there are 12 teams per division, except for the Premiership which has 14 teams and the Provincial Division 3 SE, which has 11 teams instead of the normal 12. You play each team in your division twice with no breaks, so most action goes from Week 1 to Week 24, with the year ending after week 28, for which the league cup is finished and a winner is decided. The transfer list is available from Week 1 to Week 21, who selecting and picking someone is last available in Week 20.
So, I think that is it for now. Do you think my selection would be difficult to play? Do you know of a harder position to start at? Let me know your thoughts and share your fun challenges too. I might end up trying your suggestion if they are good enough.