I have actually seen more SLEs with SEIs than with IEIs. Mirage is a very easy relationship to start, especially if you aren't fully mature. (I'm speaking from experience.)

I just ran across a video from SLE DJ Arendee, and he has somehow transitioned from an Aggressor to an Infantile who is seeking a Mother.

https://www.youtube.com/watch?v=A6muOtYWhUw

This kind of transition can happen to anyone, because I, a Victim type, can sometimes look enough like a Caregiver to attract EIIs.