#Japt, 43 29 28 bytes

##Original, 42 bytes

###Explanation Åqb £bbidbad¾dò3n)ïiaq)m¬bXibÃò ®ìG d Å :Slice off the first character qb :Split on "b" £ :Map bbidbad¾d : Compressed string "bbidbadbod" ò3n) : Partition at every 3rd character from the end (["b","bid","bad","bod"]) ï : Cartesian product ia : Compressed string "iaou" q : Split ) : End Cartesian product m : Map ¬ : Join b : Index of X : Current element ib : Prepend "b" à :End map ò :Partition at every second element ® :Map ìG : Convert from base-16 digit array to base-10 integer d : Get the character at that codepoint

Japt, 43 29 28 bytes

Original, 42 bytes

Explanation

Åqb £`bbidbad¾d`ò3n)ï`ia`q)m¬bXibÃò ®ìG d
Å                                              :Slice off the first character
 qb                                            :Split on "b"
    £                                          :Map
     `bbidbad¾d`                               :  Compressed string "bbidbadbod"
                ò3n)                           :  Partition at every 3rd character from the end (["b","bid","bad","bod"])
                    ï                          :  Cartesian product
                     `ia`                      :   Compressed string "iaou"
                          q                    :   Split
                           )                   :  End Cartesian product
                            m                  :  Map
                             ¬                 :   Join
                              b                :  Index of
                               X               :   Current element
                                ib             :   Prepend "b"
                                  Ã            :End map
                                   ò           :Partition at every second element
                                     ®         :Map
                                      ìG       :  Convert from base-16 digit array to base-10 integer
                                         d     :  Get the character at that codepoint

#Japt, 43 29 bytes

Unsurprisingly, a port of Dennis' Jelly solution works out much shorter.

Outputs an array of characters.

Åqbu)®¬®c ^1 %9%4Ãì2Ãò2 ®ìG d

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##Original, 43 bytes

Åqb £`bbidbad¾d`ò3n)ï`ia`q)m¬bXibÃò2 ®ìG d

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###Explanation Åqb £bbidbad¾dò3n)ïiaq)m¬bXibÃò2 ®ìG d Å  :Slice off the first character qb  :Split on "b" £  :Map bbidbad¾d  : Compressed string "bbidbadbod" ò3n)  : Partition at every 3rd character from the end (["b","bid","bad","bod"]) ï  : Cartesian product ia : Compressed string "iaou" q  : Split )  : End Cartesian product m  : Map ¬  : Join b  : Index of X  : Current element ib  : Prepend "b" à  :End map ò2 :Partition at every second element ® :Map ìG : Convert from base-16 digit array to base-10 integer d : Get the character at that codepoint

#Japt, 43 29 28 bytes

Unsurprisingly, a port of Dennis' Jelly solution works out much shorter.

Outputs an array of characters.

Åqbu)®¬®c ^1 %9%4Ãì2Ãò ®ìG d

Try it

##Original, 42 bytes

Åqb £`bbidbad¾d`ò3n)ï`ia`q)m¬bXibÃò ®ìG d

Try it

###Explanation Åqb £bbidbad¾dò3n)ïiaq)m¬bXibÃò ®ìG d Å   :Slice off the first character qb   :Split on "b" £   :Map bbidbad¾d   : Compressed string "bbidbadbod" ò3n)   : Partition at every 3rd character from the end (["b","bid","bad","bod"]) ï   : Cartesian product ia : Compressed string "iaou" q   : Split )   : End Cartesian product m   : Map ¬   : Join b   : Index of X   : Current element ib   : Prepend "b" à   :End map ò :Partition at every second element ® :Map ìG : Convert from base-16 digit array to base-10 integer d : Get the character at that codepoint

#Japt, 43 bytes

More golfing to follow ... hopefully.

Outputs an array of characters.

Åqb £`bbidbad¾d`ò3n)ï`ia`q)m¬bXibÃò2 ®ìG d

Try it

##Explanation Åqb £bbidbad¾dò3n)ïiaq)m¬bXibÃò2 ®ìG d Å :Slice off the first character qb :Split on "b" £ :Map bbidbad¾d : Compressed string "bbidbadbod" ò3n) : Partition at every 3rd character from the end (["b","bid","bad","bod"]) ï : Cartesian product ia : Compressed string "iaou" q : Split ) : End Cartesian product m : Map ¬ : Join b : Index of X : Current element ib : Prepend "b" à :End map ò2 :Partition at every second element ® :Map ìG : Convert from base-16 digit array to base-10 integer d : Get the character at that codepoint

#Japt, 43 29 bytes

Unsurprisingly, a port of Dennis' Jelly solution works out much shorter.

Outputs an array of characters.

Åqbu)®¬®c ^1 %9%4Ãì2Ãò2 ®ìG d

Try it

##Original, 43 bytes

Åqb £`bbidbad¾d`ò3n)ï`ia`q)m¬bXibÃò2 ®ìG d

Try it

###Explanation Åqb £bbidbad¾dò3n)ïiaq)m¬bXibÃò2 ®ìG d Å :Slice off the first character qb :Split on "b" £ :Map bbidbad¾d : Compressed string "bbidbadbod" ò3n) : Partition at every 3rd character from the end (["b","bid","bad","bod"]) ï : Cartesian product ia : Compressed string "iaou" q : Split ) : End Cartesian product m : Map ¬ : Join b : Index of X : Current element ib : Prepend "b" à :End map ò2 :Partition at every second element ® :Map ìG : Convert from base-16 digit array to base-10 integer d : Get the character at that codepoint