4DOS has support for many magic variables as does current command processors (think CMD.EXE instead of COMMAND.COM). Consider adding support for some of them optionally compiled in. (Can this be done in a manner that doesn't bloat FreeCOM?)

Please add comments with any particular "internal variables" that are likely to be broadly useful:
e.g.:
%_CPU - to get if current computer is 386 or not
%_LASTDRIVE - last available drive letter
%_ANSI - is ANSI loaded, i.e. can ANSI escape sequences be used
%@name[file] - to get base portion of a filename
%@ext[filename] - to get filename's extension
%@path[filename] - to get filename's path excluding filename

or versions
%_DOSVER to get the OS version
%_DOS to get the operating system
%_4DOS to get the 4DOS version <-- use %_FREECOM maybe? or %_CMDVER

or other commands
%@Label[drive] - get drive's volume label, i.e. to do different things when ran on different drives or basic safety checks