They've changed it now so you only need to wait for a full transfer window so he'll convert in Feb if he plays in the first half of the seasonI don't think we will get more than 2 slots for a while, it might even drop to 1 soon.
Bergvall will only need to step on the pitch for 1 minute to qualify, in fact, he will qualify if he is only named in 1 match day squad and we qualify for the conference league (or a higher UEFA comp), however we have to wait 12 months to convert him to a none ESC player.