Can the prosecution put up a token defense at pretrial and then challenge more during the actual trial? Such as suprise witnesses (FL woman) or additional evidence. Or is that just perry mason stuff.
I think they are pretty much locked in. I could be wrong.
Sure. Happens all the time. You can keep producing new witnesses up until the time you hear the words, "the defense rests". You have to give the other side fair notice, and if somebody pops up in mid-trial that the defense has never heard of they're not likely to get on the stand immediately, but "newly discovered witnesses" are not an uncommon part of the process.
The purpose of the prelim is just to determine if there's sufficient evidence to go to trial. The purpose of the trial's to convince a skeptical jury that the guy needs to go to stony lonesome.