Autohiding: You need to do some serious .rc hacking to pull this off in Austerity.
You would need something that covers all the bar elements (so that moving inbetween the elements doesnt do any actions) to trigger the autohiding action (either a label, or a hotspot or something)
Then you need to make OnEnter/Leave commands to show/hide all the bar elements.

Desktop icons: check out xDesktop (run a search on this forum)

np