I don't think having 4 out would be a problem if it weren't for the fact it becomes 5 out so easily, almost anything can cause 4 out to become 5 out. This just makes things difficult for the mods to regulate each game, there would be a bunch of issues with people complaining and the mods would have to make a bunch of subjective decisions. To make things simple I feel it should just be 3-2 set with the rule of excess on specific plays, and if you run a 3-2 set and run a pick and fade or play that makes your offense temporarily a 4 out that should be ok.
To see this working, head to your live site.