Theatre missions too of course!
I believe the entry requirements should be cut to half of what they currently are, so players can choose to keep things challenging. Each total level on MabiPro is worth more than a normal Mabi level because of 2x AP, so a level 50+ could possibly be ready to challenge Int Difficulty missions intended for total 100+. Once you get a good party together, Basic will grow too easy, too
And people will be wanting to challenge Advanced long before 300!