How a later war could have strengthened Malaya's defenses

Did Malaya have stronger local forces planned before the Second World War intervened?

Yes. More time would have allowed the garrison to train larger, better-equipped local forces and develop the infrastructure needed to support them.

Malaya did have plans for stronger local forces. Another five or six years would have let the existing garrison train local formations, expand their cadres, and improve their equipment. That preparation would also have matured bases and other infrastructure before a Japanese attack. Peacetime institution-building mattered as much as adding individual ships or battalions.