You can already do this. http://www.faqs.org/docs/Linux-mini/Xterm-Title.html
> Wouldn't it be nice to show the intended completions in a popup as you're typing (like web browsers do)?
This can probably be written as an extension to bash/tcsh/zsh to use the pop-up completion facilities of vim. If you want nice webapp-looking ones, you might be able to get away with terminal escape codes and use a perl script (this is how rxvt lets you click on http links automatically).
> can the result not be folded into a single line showing the summary, that I could expand if I wished?
An interesting point, and I was going to counter with a small one-liner using 'tee,' but I couldn't think of a good one quickly that does what you really want: 'auto-collapse.' The problem with this is that often with giant lines of output you really only want to look at the last few to see what happened. Otherwise your output is typically some kind of streaming log (you do not want auto-collapse for this) or a poorly written program. "walls of text" suck and are usually an indication of something you expect to have a lot of output (looooong makefile) and can do a less accordingly, or an unexpected error. If it's an error you want to see what it is, so you're going to click on the 'expand' button -- an extra click every time on an all-typing interface kind of sucks.