We can test that theory. If we go with DW thinking this up, breaking into the house, being able to control those in it for 18 hours, killing all four, setting the fire, driving the Porsche away and torching it---how do the facts as we know them fit? And what questions would we still have? What is difficult to explain if we try to support this theory?
I'll go first:
DW solo matching up to a fact--
1) Despite numerous search warrants, interviews with the convoy gang, a nearly three weeks long investigation involving ATA, Secret Service, FBI, and police, he is the only one who has been arrested (as Kali points out)
Question:
1) Why did investigators maintain that the crimes would have required the presence and assistance of others?
2) How did DW get to the house?
I think reasonable answers could be found.
Any one else want to take a whack at this? Include motive, what the plan might have been initially, logistics, evidence we know about so far, and account for any known facts, witness statements, LE statements while we all acknowledge discrepancies will exist, lots of stuff we don't know yet, and LE well might be revising earlier thinking.
We should be able to put together a good theoretical case between us for DW having acted alone--except for whatever practical assistance he was offered by unwitting pals post-crime.
Posing hypotheticals only (PHO)