Bash is pretty capable as shells go. It's the default on most Linux-based systems, and has incorporated a lot of features that made other shells (e.g., ksh and zsh) once attractive. From where I sit, I think there's not much advantage to using other common shells over bash (tclsh is really an interactive Tcl prompt, not so much a substitute for a proper shell), although I use to like ksh93 only because it tends to be cleaner and more consistent. Often, specific functionality that is confining in bash (or any other shell) is better served by another utility. CDP includes several utilities for manipulating tables of data, for example. You could extend your capabilities here by writing awk scripts (or perl, if that's your thing) for these kinds of problems. Note lists can be produced by almost anything (try generating random numbers in R, for example). Pretty much whatever you're comfortable with is game. I do miss the PC GUIs, though, and hope one of them makes it over to Linux before long.
As you say, realtime systems are often surprisingly "slow"! On my desktop, CDP renders all but larger sounds almost instantly. Sculpting a sound following an iterative trial & error process is something that I find typically more rewarding and less painstaking in CDP than most other systems I've worked with, allowing me to learn more by the simple fact that I can usually do many more trials than other systems might allow in the same span of time. I consider it an absolute luxury to be able to render a two minute long sound in "high def", and having it ready for audition in five seconds (or less). The old tape practitioners would be more than a little envious!
I like your idea of using Renoise as a workspace. I do something similar with Harrison Mixbus, sometimes. But, generally, the fewer tools I can get away with, these days, the better. Failing a well integrated front-end, I'll take "simple." In lieu of a work environment packed with more gear and software than anyone could possibly learn to use well in a lifetime, how many distractions can I cut away and still results I'm proud of? A top-notch DAC & good headphones might be a given, but do I even need a particularly good computer, anymore? Maybe not. The road to gain enough know-how to really use everything effectively will be a long one for me. But it's been interesting and oddly liberating!
If you don't already own them, I highly recommend Trevor Wishart's Audible Design and On Sonic Art. I found these books useful and inspiring.