I was thinking yesterday when I was researching materials needed for Miasma Whip 2. It needs Iron Ore (easy, just go to caves lvl 2 in an Abandoned town) and Cherries. Now, Cherries are unlocked by killing all enemies on a surface chunk of a certain time "while Overlord forces are at Tier 2". See the bolded part? If it really works that way, it's quite easy to screw yourself out of cherries and blocking everything that requires them, unless it's "T2 and above" in the code.
I'm not at home to test right now, but how does it work? If you don't unlock them at T2, are you screwed then? If so, that should probably change, unless you want people to spend their life reading the crafting grimoire like the Bible to make sure they didn't miss an unlock.