You're missing a marketing opportunity here, build a large, ill fitting ugly iem with a 10mm isobaric DD, large 14.4mm planer, 6Ba's, two EST's, a handful of microplanars and build a cable using 10AWG copper cable terminated in a mini xlr to attach to the oversized IEM shell, obviously you'll need a full size XLR plug on the other end to plug into a massive headphone amp.
Obviously it'll sound totally crap but that's what folk on here will decry as "novel, esoteric, not for everyone, unique, needs careful pairing, needs time to appreciate the nuances" etc...etc.
There you go, I expect it'll sell for $9999, I'll take 5% for giving you my idea.
We have a pentabrid experiment in the backburner that sounds terrible.
I should release it as a Project, dump all the technical specs, and never publish the measurements. Call it Project Flex or something.