Oh I agree the mac and lisa were infinitely more accessible than the II but they could've at least made some concessions earlier than they did (I don't think any of the macs had an expansion bus until the II)
The SE has a single NUBUS slot which is how we installed the Ascente ethernet cards. I would say the SE is probably the same generation of the II. I think the II the SE and the CI were probably all the same generation. I also think the II's code name was the Open Mac.