Too spread out
No - it is too spread out for that. NOt sure which SM you are referring to:
Space Mountain to Jungle Cruise, without a crowd there, takes about 5-6 minutes in each direction, walking or semi-running very quickly. With a crowd, it takes longer than that - and sometimes the wait AT Space Mountain can be 5 - 10 minutes depending on how many of the fast pass machines work, how many do not, and how many people are waiting to fast pass.
Splash Mountain and Big THunder Mountain are about the same time, although it is closer - still, you have to weave around the southwest portion of the park, always very congested. Probably 10 minutes back and forth PLUS however long you need to wait to fastpass.
NOTE: Fastpass is not instantaneous - you need to wait in most cases. Sometimes a minute, sometimes 10 depending on the attraction. SOARIN at epcot has amazingly long waits for the fastpass machines.
Have you taken a look at the Unofficial Guide to WDW 2006? Their touring plans actually work - and they are broken down by people alone, people with kids, adults only etc. The Magic Kingdom is larger than it looks, much much larger than its California equivalent, and the crowds make it next to impossible to travel quickly from one point to another.