I'd do it in place like so:

Use dremel tool to surgically grind BIG slot for 3/8 socket flat head screwdriver bit. Face shield and PATIENCE necessary.

NOTE: 3/8 socket large flat slotted screwdriver is _ONE_ PIECE and blade is LARGE (not a screwdriver bit pressed into a socket base)

Use small bottle jack to firmly hold ratchet into newly (possibly irregularly) ground slot so it grips and won't twist out.

Remove plug.

DONE.

Socket looks like this but instead of chunk of square metal it has a flat head screwdriver blade. Width of blade equals width of socket base. If you can't find it at Sears, make your own from what's shown below and bench grinder (though blade will be less wide it will probably still work, use 1/2 drive to grind a wider blade).

P.S. I don't think easy outs or screw extractors work very reliably in aluminum alloys.