When I use :FORCE, in most cases I do want to recompile solely the
specified system, not all its dependencies.
In my ideal world, :FORCE T would recompile the specified system only,
and :FORCE :ALL would recompile it along its dependencies.
Of course that would be backwards-incompatible, so perhaps better stick
with the current behaviour for :FORCE T, but add :FORCE :SYSTEM, or
:FORCE :SHALLOW, or similiar.
-T.