Paired kata
I've stayed out of this mostly because I am too junior to know a lot but Koryu other than MJER do include paired kata much earlier than 6 dan and many that I have seen teach Kihon in this manner. Waiting until a person has perfected drawing a sword before teaching him to use it is akin to teaching a person to draw a gun for 20 years before you give him bullets to shoot it. It just isn't all that smart. Now how does this apply to iai???? Depends on what you want out of it. I like MJER it has a fluidity and grace that many martial art don't have without loosing any semblance of being "Martial"
Suck, Squeeze, Bang, Blow...
...that's what makes my thumper go