Re: emacs compatibility - changing a default binding?

Note further: rather than make this a compile-time configuration
option, why not use the opportunity presented by the "splash screen"
to allow people to choose:

[Press Space or Return to end.]

could be replaced by:

[Press Space for legacy command binding (C-a) or Return for a more
modern command binding (C-\).]

People who start with screen -q would presumably be happy to accept
the default (or whatever is in their .screenrc).