So... what we should do now is to work out all the things Quirrell should have before this. He couldn't predict partial transfiguration, true. But he knew that Harry had a power he knew not, and had a long time to plan for contingencies.

Personally, I think he should have had the death eaters disillusioned, surround Harry but from a distance, cast holograms to confuse him and then use ventriliquo charms. At the very least disillusionment should be as much of a general tactic as a massed finite and the death eaters could have been hidden.

The massively more obvious solution is just to kill Harry quickly, and moreover to not EVER offer the protagonist 60 seconds to try to save himself, no matter how interesting that sounds.

Any other general/specific tactics that LV could and should have thought of in advance? He had an entire year to plan this, and has Harry level intelligence. He should have predicted and outplayed.