given where you are...the local road base would be fine. Just placed it and compact it. We had a driveway and parking area made of it on a block of low ground close to Tuggerah Lake - worked a treat and survived a couple of floods no worries.
Never heard of mixing cement with it (you can't buy concrete in a bag - only cement with sand and stones in it!!) though....and if it's over a soft substrate then it'll crack anyway.
If you can source some reclaimed asphalt (which is available in your part of the world) from roadworks to place over the top (about 25 -50mm) and roll again....you'll have a nearly bullet proof car park.