San Diego’s efforts to boost emergency response times in the sprawling and increasingly congested city would take a big step forward under a new compromise proposal. The proposal, created by the city’s independent budget analyst and endorsed by leaders of the Fire-Rescue Department, would boost response times in “gap areas” more quickly and cheaply than building all of the additional fire stations recommended last month by a consultant. The proposal includes covering six of 12 geographical gap areas with fully staffed new stations in the next few years, and covering the other six areas less aggressively with “peak hour” engines until the city can afford new stations there.