I don't think anyone in your Division played in the Cup, so really, everyone you are competing against this season is in the same situation as yourself, this would make it fair wouldn't it?
I am in a division that is playing in the Cup and I have 6 teams that decided to invest their initial cash into competitive players and not into player development or arenas , they are carrying higher salaries and need the Cup just to make ends meet, sure they are bringing more money in each week, but if they keep going this far in the Cup and don't invest elsewhere, what will they have when they promote? Will be interesting to see... As for Divisions like yours where you can spend less on higher salaried players, train a bunch of guys and pour in your cash to a bigger Arena and still have the same chances of promotion, I guess it remains to be seen just who will survive better as the promotions happen.
If I were in one of the Divisions not playing I would be looking at the opportunity that I have and how to make it work, you never know, maybe the temptation of playing in the Cup and continually throwing more and more resources at it for the limited returns, might just show to be a limiting long term strategy??