This is an interesting idea--that in a reimagined OS, programs could have their output connected to all sorts of sinks (terminal, file, GUI, web content) without carrying baggage related to those sinks' behaviors.

I think the core question is whether some middle layer of output processing between program and sink/display could be created that knows enough about (using terminals as an example sink) raw mode/console dimensions/buffering to make most programs display correctly enough for most users without knowing specifics about the program writing the output's internals. If that can be done, then programs that need more specifics (e.g. complex animated/ncurses GUIs) could either propose overrides/settings to the output middleware or configure it directly, and programs that don't wouldn't.

That's possible to implement, sure, but can that be done without just reinventing the POSIX terminal API, or any one of the bad multiplatform-simple-GUI APIs, badly?