I assume you mean what if the Japanese economy did not stall out after the bubble burst and kept its 80s growth rate, rather than what laws could Japan pass to keep its real estate prices sky high and prevent a rational revaluation.
If the real estate bubble popped just 18 months to 2 years before it did in real life then the damage would have been small enough that Japan might have had a normal recession. Not paralyzed with an economic disaster, Japan makes a move to reform the Banking system.
There are two ways that Japan could have grown. It could have reformed its inefficient domestic market or it could have had more industrial policy winners. The path of least political resistance is that domestic markets rationalize gradually, but the really growth coming from new Industrial champions.
So imagine a Lexus strategy of Japan having more high end manufacturing which displaces high end German manufactures trading on Japanese price and reliability rather than German craftsmanship.
Japan would also have to get a big piece of the computer, cell phone, software, and telecommunication boom. In real life MITI (the bureaucracy that picked winners and losers) was blind sided by the pace of change in the 90s, but Japan could have conceivably had many more winners than in OTL.
Finally, Japan is the leader in commercial and hobby robotics. This field, like bio-tech is still more promise and expensive investment than big payoff, but lets suppose while America was crashing in 2008 a robotic revolution was starting to take hold in Japan.
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So how would a confident Japan be different with a super-sized economy? It would be more assertive, especially regarding threats such as North Korea. One can imagine a joint US-Japanese anti-missile shield. Japan would balance China rather than being overshadowed by it.
Japan would still be known for (to Westerners) strange fads, but the hobbies would be more expensive and flamboyant. Japan would be, with the United States, a world taste-maker.
A robotics revolution would turn Japan's greatest weakness into its strength. Robots would solve Japan's labor problems, help care for the old, and also help pay for the old through labor saving productivity. Although foreigners would be fascinated by the robotic future already taking clear shape in the Japan of 2011, most countries lacking Japan's social consensus and tight labor markets would feel that in their case that the obsoleting of nearly a third of their national workforce will lead to a social disaster rather than Japanese style balance and progress. China specifically has warned about the threat of a "Terminator Future" after being alarmed by the new Japanese economic model which threatens to swamp China's hard won old style economic gains.
Of course Japan continues to have many problems but no one has doubted since the 1980s that Japan is the nation best positioned to prosper in the future. As both former Japanese Ambassadors Walter Mondale and Colin Powell have stated. "U.S.-Japan relationship is the most important in the world, bar none."