If it was me and I wanted to be sure my 500k was there in 12 months plus interest then I would go 100% into 4 separate bank accounts and get 2% interest.
Everything else is risk. Like others have said, the market can and has done previously sunk 20, 30 or even 55% in a matter of 12 Months. Do you really want to risk your 500K in the sharemarket? I'm not saying that it is not a viable investment, I'm saying what will you do if turn your 500k into 250K after being caught in a market crash?
Disclosure: I hold the VHY ETF, I know the risks and I can handle a 50% drop if it happened overnight.
That is probably the question you should be asking yourself. Anything can happen in this crazy world of ours, good luck.