To make fundamental changes to the design or structure of something.
"The workshops are headed by Women Services counselor Jane Maxwell. She feels there is a need to have these workshops available for women of all backgrounds because sometimes women suffer from both self-esteem and assertiveness issues.
'I want women to rearchitect themselves — focus on the positive aspects of themselves and get rid of the negative,' Maxwell said."
—Andrea Parker, "SIUC hosts self-esteem workshop for women," University Wire, July 11, 2001
"What he really wants to do, he says, is 'rearchitect' the market. It was something he achieved at Mars with the Mars Bar ice-cream, an innovation which many thought couldn't work and, if it did, would cannibalise the sales of chocolate Mars Bars. It didn't and went on to become a hugely profitable line, selling at twice the price of normal choices. In similar fashion, he wants to turn the accepted model of the clothing market on its head."
—Andrew Davidson, "Allan Leighton; interview with the Asda CEO," Management Today, September 1997
Today's bit of verb-iage comes to us by way of the technology industry, which never saw a noun it couldn't turn into a verb. The pocket protector crowd have been using this verb for a long time, but the Word Spy's interest is in non-technical usage, as in the above citation.
Just for the heck of it, here's the earliest use I could find for rearchitect in a technological context:
"That's probably the biggest reason to rethink, rearchitect whatever you want to call it systems we have now, even those that are fairly new."
Wayne Rhodes, "Whatever will be will be," Infosystems, March 1987