Suggestion: noInternalPointers property

[dsimcha]

As I've mentioned previously, D's partially conservative garbage collection is
often a significant limitation for me when working with large amounts of data.
 As a workaround, I'd like to suggest that the GC be given a
noInternalPointers function.  When called with a pointer to the start of a
block, it would tell the GC to only consider pointers to the start of the
block, not internal pointers.  This would prevent false pointers from wreaking
havoc on large data structures.  In exchange, you'd have to be careful that a
reference to the start of the data structure was somewhere on the stack.  Of
course, you could still pass internal around all you wanted as long as you
didn't try to return an internal pointer from the function that allocated the
data structure.

The noInternalPointers property could also be a property of builtin dynamic
arrays.  Appending a large amount of times to a large array breaks the GC in
the current form because, when the array gets reallocated, the old memory
blocks are not necessarily cleaned up due to the false pointer problem.  If an
array has the noInternalPointers property, every time it is reallocated due to
resizing, the pointer to the start of it would be automatically marked with
the noInternalPointers attribute.

Does all this sound feasible/reasonable?