If you want a really strange 'hybrid' valve, look at the EFM1 - a tuning indicator built into the same bottle as an audio variable μ pentode.
http://www.r-type.org/exhib/aaa0982.htm
What were they thinking??
It even had a follow-on!
https://www.radiomuseum.org/tubes/tube_efm11.html
using the strange German base with the pins non-synnetrically arranged round the central spigot.
That there were no Octal/Loctal/B8/B9 successors shows that such things failed to capture the imagination of radio-designers.