So, basically:

• Crustaceans is like reptiles, a paraphyletic group that does not include a whole clade
• Pancrustacea was coined to include the crustaceans and hexapoda (insects, bristletails, coneheads, springtails)
• The sister clade of Hexapoda is the Remipedia clade. The remipedes are really weird for crustacean standards, as they’re venomous and live in caves

I still predict the last common ancestor of all hexapoda to be terrestrial, because this might explain why the Hexapoda got so bloody huge - it found/founded a niche no other Pancrustacean was adapted for, and it spread like crazy.