The main reason for making a bash builtin would be simply for perfomance. This effectively allows you to have C bindings in bash, so for example, you could create a JSON parser/sorting algorithm in C, compile it as a bash builtin, and write scripts around it, which would allow you to do things that usually you'd use jq for, but much more efficiently.
git clone https://github.com/644/ldnsbash; cd ldnsbash; make; enable -f ./ldnsbash.so ldnsbash; ldnsbash; echo "$LDNSBASH"
git clone https://github.com/644/ldnsbash
cd ldnsbash
make
enable -f ./ldnsbash.so ldnsbash
ldnsbash
echo "$LDNSBASH"
enable -d ldnsbash
It's important to have bash >4.0+ installed, along with bash-builtins.
MIT