Hey there, sorry for the very late reply, for some reason I didn't receive an email notification about this post...
I've thought about this before, but decided it's mainly going to add more unnecessary clutter because the current idea is that "bigger terminal = higher security level and corresponding detection chance," so you can differentiate them visibly. Maybe you hadn't noticed that it's not random at all--there are a static handful of terminal types and all those that look the same share the exact same stats which follow that general rule of progression, making it pretty easy to have a good idea of whether or not you're equipped to deal with a given terminal.
This is why, for example, if I'm a combat build without any hackware I'll almost certainly ignore the really big terminals unless I happen to be passing right next to it and maybe can hope for a 5-10% direct hack to throw a couple of attempts at.