One question though: Do you really need 1000+ lines of shell scripts? I almost have 20 years with shell scripting and I still have the rule of not writing long

One question though: Do you really need 1000+ lines of shell scripts? I almost have 20 years with shell scripting and I still have the rule of not writing longer than 1-2 page shell scripts and use something else for longer projects or break it down to much smaller chunks and invoke the parts with a main.sh. Fish is a for making software engineering and system administration easier by having functionality like command completion (without tab) and it works like a charm. I would never ever would nother to rewrite my bash scripts in fish simply because bash is on all the servers and fish is on none by default. I am not sure what you are trying to solve here but good luck.