.....The struggling sandwich chain has seen customer traffic plummet a whopping 25 percent over the past five years.... In a Nov. 30 memo to franchisees that revealed the stomach-churning drop, Subway’s owners promised $25 million to boost marketing this spring for the company’s 44,000 locations and to bring back a limited-time, $4.99 footlong sandwich promotion..... ....the crucial footlong deal — aimed squarely at the McDonald’s dollar menu — is in danger because of a revolt by franchise owners, who fret that doubling down on discounts will further shave their already thin profits. More than 400 of them have signed a...