keep static terminal size
Constant terminal resizing doesn't work well with many full-screen programs. Yes, Termius does a great job of notifying the remote host of window size changes, but it still confuses so many programs, even on Linux :)
I used to use PuTTY for Symbian and that thing kept the window always the same size, all the on-screen pop-ups and menus with configurable special key shortcuts popped over the terminal so I could quickly "press" home/end/alt-something/^R/whatever and nothing blinked or broke.
It also had the option not to react to phone orientation, even if the phone was set to rotate the screen - this is trivial to lock manually in the phone's settings/notification bar, but would be nice in Termius itself.
For touch screens, good work-around would be to keep the keyboard always on + locking rotation. As long as all the shortcuts always take up the same space as the keyboard, it will never have to resize.
Better solution [for when I finally get a new Blackberry ;)] would be actually providing a way to have a virtual screen with size set for a Host/connection (for example 80x25) and make it a pinch-zoomable and scrollable window that can get pushed around when menus/keyboards open.
For physical keyboards, the solution from that old PuTTY would also be awesome - double-tap for a semi-translucent menu in the middle of the screen, instead of taking 1/3 of the screen for a 4x4 grid with shortcuts, as it is now.