SBA TRACON Controller reported issuing an incorrect clearance which delayed an aircraft turn to avoid entering a higher MVA resulting in a CFTT event. SBA Controller stated that a redesign of MVA's is needed to allow offshore aircraft lower altitudes.

Narrative

Aircraft X was being vectored northbound at 040 for the RNAV (GPS) Runway 07 approach behind Aircraft Y 1000 feet below him and less than 3 miles. Both aircraft were on extended vectors to allow Aircraft Z to depart opposite direction due to a flow window and strong wind favoring Runway 25. Both aircraft were at least 7 miles offshore at this time. The expectation was that Aircraft Z would expedite their climb through 050 (as instructed) to get above Aircraft X; while Aircraft Y would be angled in to build the necessary separation to bring Aircraft X behind. Aircraft Z took longer than expected to climb; so I needed to bend them to the south to get Aircraft Y in towards the field. This put Aircraft X closer than desired to a 041 ft. MVA; and I instructed Aircraft X to make a left turn to the initial approach fix for the GPS - but I accidentally swapped the IAP between the RNAV and ILS approaches. The resultant confusion likely delayed Aircraft X's turn; and once I observed the proximity I issued the climb to 041. Unfortunately; Aircraft X turned and climbed too late; and entered the MVA at 040. The weather at the field was 004 SCT and 006 BKN. At no point did Aircraft X proceed onshore at 040. Our MVA's are built such that aircraft are consistently high on the approach and our weather conditions frequently require that we launch aircraft opposite to the arriving aircraft traffic pattern. There are no obstacles offshore for aircraft to be concerned about - our MVA's should reflect this; and be rebuilt to allow arrivals to descend to a lower altitude while off-shore.