I don't like C-like syntax in Unix tools, as the shell isn't C-like, and it's not clear that it's possible to make it C-like without sacrificing writing speed (lots of parentheses are hard to wrangle interactively); and awk is nice and efficient for some things the shell can't easily do, but it's its own world with a different set of variables and overlapping functionality, and you can't easily stick a pipe in the middle of an awk program. My ideal redesign would take the shell, make the syntax for iteration, pattern matching, arrays, etc. much simpler (integrating the functionality of awk), and (most importantly?) unify the ways various commands expect to receive data and take arguments representing parts of that data (fields, lines)... while still being the shell.

Dunno about sed - once I wrote a Brainfuck interpreter in it for fun, but I see it as a Turing tarpit - for things more complicated than "/a/s/a/b/" I prefer awk, though I wish awk had the succinct "s/a/b/", and I wish either of them had a quick way to extract a capture group from a match. (vi was a teenager when I was born, so I personally don't care about adhering to ed.)

I've never tried any APL-like languages and am therefore somewhat scared of them... but most of the programs I write outside of the interactive shell are non-throwaway and/or the kind of glue code that uses lots of random system functions, which decreases the value of extreme terseness. (But I prefer anything over Java and dislike the inflexibility of languages without macros, so perhaps it's only logical for me to go ahead and learn an array language.)