Why the Veil? (as plot device)

[lavaluvn]

No: HPFGUIDX 77789

Beg pardon if this has already been discussed - I couldn't find a 
thread, but I'm only recently back after a long period of post-OotP 
mourning.

My question is: why did JKR use the veil for Sirius' (sniff) death?  
I ask because because my husband (who has only read the HP books 
once - can you imagine?- and hasn't read any of the JKR interviews) 
had the reaction - "oh he'll be back" after reading the part with the 
death.  "What? What makes you think that?" I asked, faintly 
hopeful.  "Well, there's no body! Nothing to make it final."

I know everyone quotes JKR on how death is final, etc, etc, no one 
can come back.  The conversation with NHNick would seem to support 
that.  But in this case we have no obvious proof of death, other than 
the word of DD and Lupin.  Why did JKR make it such a vague, 
metaphorical death?  Why not just have him get AKed and make it 
really clear that he's dead?  Why the elaborate set up with the death 
chamber, voices, etc?  Here's a few possibilities I've thought of... 
any others would be highly appreciated.

1. AK has been used for one death already, just needed something 
different.
2. She didn't want to deal with the logistics of Sirius' body being 
discovered in the MOM.  Who gets the credit/blame? What about the 
funeral?
3. She's leaving open possibilities for Sirius to return in some form 
or other.  (I know, wishful thinking)
4. She's setting up the Veil for some future role (I believe b_boy 
had some vision of it being used on Voldemort in the end?)
5. ???

Thanks,  CAG