I was trolling through gnome-terminal bugs and noticed this nice mockup by Allan Day for merging the Preferences and Profile Preferences together. This would actually be pretty easy to do in Terminix given the current code style.
Mockup:
https://bugzilla.gnome.org/attachment.cgi?id=266172&action=edit
Bug Report:
https://bugzilla.gnome.org/show_bug.cgi?id=722114
Looks great!
I've taken a first cut at this, seems to be working pretty well. There are a few things left to clean up as follows such as renaming a profile should rename it in the list and the title. Anyway, here's a screenshot showing what it looks like so far.

How about changing the "Add Profile" button to look like NetworkManager dialog to add/remove networks?

Yeah that makes sense from a consistency point of view...
...lol but you could have suggested it before I wrote the code! :)
And in case it's not clear, I'm just joking on that last post.
Done:

OK I think this is basically done. If there are problems, and I'm sure there, just open new issues for them and I will deal with them.
Amazing, good job!
Most helpful comment
Done: