"Snape," the Pensieve, and Memory Modification

[telcharii]

No: HPFGUIDX 72737

I'm new and therefore not sure whether I'm doing this right, but here 
goes....

Has there been some thought given to the possibility that Snape's 
worst memory is dangerous, and therefore must be hidden in the 
Pensieve, because it is not really Snape's memory?

One solution to the is-the-Pensieve-objective-or-subjective debate 
might be that SWM is actually a combination of two people's memories, 
or a memory-modification attempt that didn't quite succeed.  This 
might explain all the differences in perspective, and Snape's 
seemingly encyclopedic perceptions.

There are at least two possible motives for such memory work.  The 
more plausible motive is to create a mental background for Snape that 
justifies a hatred of Potters if any Legilimens reads Snape's mind.  
This would have been part of Snape's preparation for spying.  But 
then, you logically ask, if Voldemort already knows that Snape was a 
spy, why is evidence of memory modification still dangerous?

Which very logical question brings me to the second possible, and 
truly wild, motive: perhaps this memory work was done in order to 
conceal the fact that Snape is not really Snape.

Remembering that memory spells are Charms (Lily's forte), it's 
possible that many moons ago, Lily did some memory work on the person 
we think is Snape.  The logical victim would be James, who of course 
has a wand built for Transfiguration.  This would explain 
why "Snape's Worst Memory" appears to conflate Snape's and James's 
perceptions.  

Perhaps Professor Snape is actually James Potter.  And Snape took 
James's place that night in Godric's Hollow.  And James has been 
trying to harry and hate Harry for four years in order to ensure that 
no one thinks that they might be related.

Biggest flaw with this notion: the Marauder's Map.  But then "Snape" 
saw it very early on, and as a maker of the Map, might have known how 
to defeat it.