Since there's been a lot of questions about the runtime library, its changeability, and the need for one, let me bring up how I picture this being handled.
Moving from Action on the Atari to Turbo Pascal on the PC back in the 1990's, I grew to love the way it handled what TP calls Units, as compared to the INCLUDE system used by Action and C. I think I want to bring a degree of this to the new language.
I picture breaking the RTL up into segments, each handling a different area. We could then have the first statement of a program or segment of code be one telling the compiler which "units" of the RTL are used by the code that will follow.
For example, the first statement of an ACUSOL program might be along the lines of
This would tell the compiler that the program uses routines, variables, or classes defined in files called DOS.ACU, SOUND.ACU, PMG.ACU, and DISPLIST.ACU (for disk routines, sounds, player-missile graphics, and custom display lists).
This would also allow us to have "units" of code that require code from other units, and have the compiler know what it needs to compile from each. Let's say you have units called TEXT and STREAMS, both of which require DOS routines. Those two units would have USES statements that reference DOS. Upon loading the first unit, the compiler would know it needs DOS, and that it already has it when it loads the second unit.
This way you don't have to remember that certain segments require others, and we won't end up with multiple INCLUDEs by accident.
INCLUDE will, of course, still be supported for backwards compatibility.