Maybe those requirements could be tied to the difficulty chosen by the player. I managed to make do with level 1 promotion just fine, so personally, I'm fine with those requirements.
I mean there is no problem with requirements, even set "release a single" as the requirement also. It just should be higher level of promote. It makes sense to be above the level 4, but not be level 2. Since we need to release a single for higher level of promote now, it MUST be fine to do with level 1 promotion. :p