Good to know. I was coding on DOS in the 80s and didn't really do anything with unix until the early 90s. I vaguely remember vt100 now that you said it, but I did so little I had to look them up every time I did one. I coded a couple of programs in VI over a terminal, but that was so bad that I figured out a way to do it on windows and paste it into the terminal and save it, I gave up trying to edit like that.
batch files are not terribly safe, but they are NO WORSE than the attacker having the ability to type dos commands at a console with whatever level of permissions.
again, use of system(anything) is the problem, not 'cls'. So any code with system in it would fail if you ran it through a vulnerability check program, and could be hacked by a determined bad person.
I don't know another way to change screen size, but same as clear screen, there are probably 50 ways to do it. See if you can find something with a search as we did for clear screen. If you can't, I can try to look it up and play with it but I am busy this week.
I don't know why your winx can't run the vt codes. I will research that when I can as it is odd. In the meantime, make sure you have all the updates.