Daylin inc., a 300 million los Angeles retailer that was in deep financial trouble two year ago, asks each product-area manager to draw up a five-year plan to assess his unit’s competitive position, and spell out a set of actions to enhance it. William M. duke, planning director, credits the two-year-old system with substantially boosting profits at Daylin’s handy Dan home improvement centers, for one , and with bolstering Daylin’s fortunes as a whole . success has come at a price, however. At the company’s Diana fashion stores division