Yes, the ~exec function is in fact an interactive shell, but with horrible output, so you'll want to get a remote shell.
Agreed. I was just thinking of the non-technical end-users of the existing Screensaver and Fonts hacks. Expecting them to first establish a remote shell to install the screensaver hack would be a bit much. However, typing ";debugOn" followed by a short "~exec ss-install.sh" wouldn't be nearly as hard to create instructions for.
I almost wish I had a K3 to experiment on now.