; overload extrn to reduce size of obj
macro extrn s {
  match str =as nm:=dword,s \{
    if used nm
      extrn str as nm:dword
    end if
  \}
}    

public YouAreHere as '_Impressive'

YouAreHere:    

extrn '_Impressive' as NotThereYet:dword

call NotThereYet    

It seems like you were just making note of a deficiency in NASM that caused difficulty in your unified approach.

by the way, why do you place that ":DWORD" everywhere?

; overload extrn to reduce size of obj
macro extrn s {
  match str =as nm:d,s \{
    if used nm
      extrn str as nm:d
    end if
  \}
}    

By that statement I assume it is the default. I have never liked data size defaults - more so on an interface. I doubt Tomasz would change the default and most all will be DWORDS; but I do have some :BYTEs. Should maybe change the macro:

label1 dd 10 ;dword size assigned
label2:   ;no size assigned
    dd 10
cmp [label1], 10  ;we know label1 is dword, so this compares dword
mov [label1], eax ;OK, moves to dword at label1
mov [label1], ax  ;error, ax is word and label1 is dword, use following
mov word [label1], ax ;OK
cmp [label2], 10  ;label2 has no size assigned, this throws error
mov [label2], eax ;OK, both eax and label2 are dwords
mov [label2], ax  ;OK, moves to word at label2
    

Default is label without any assigned size.

        mov     ecx,eax
        call    [ExitProcess]     

  kernel_table:
    ExitProcess dq RVA _ExitProcess
    dq 0
    

vid, check your example in fasm to see if all comments are true