Bash terminal on tablets
Yes, to an extent. I know there are apps that will create an SSH terminal. Most likely there are other apps that can process other types of protocols.

There are only few tablets that compatible with Ubuntu (At least work well with). The Nexus 7 and/or 10 being a prime example. From what I hear, it works very well and is almost no different from the desktop version.

In my opinion, from what you are looking for, I'd get a Nexus 7/10 and try out Android OS, and if it can't do everything you want it to, then install Ubuntu.