I don't have personal experience with a teenage part (yet?), but my EMDR T sometimes combines EMDR with parts work, which adds an interesting dimension to both the EMDR and the parts work. I already can't explain EMDR, so explaining EMDR + parts work together is beyond me, but there is something about the integration process that makes accessing the parts easier. It's like you're already in a state of reactivation so the raw trauma stuff is right there, but you're also reprocessing things so the pain feels more controllable (or just less scary to re-experience?). So you're probably not asking about adding another therapist with EMDR and IFS expertise, but if you're really wanting to get creative eventually, this could be one option.